U.S. patent application number 14/887244 was filed with the patent office on 2016-02-11 for systems and methods for uplink signaling using time-frequency resources.
The applicant listed for this patent is Apple Inc.. Invention is credited to Mo-Han FONG, Jianglei MA, Robert NOVAK, Sophie VRZIC, Dong-Sheng YU, Jun YUAN.
Application Number | 20160044656 14/887244 |
Document ID | / |
Family ID | 40451521 |
Filed Date | 2016-02-11 |
United States Patent
Application |
20160044656 |
Kind Code |
A1 |
NOVAK; Robert ; et
al. |
February 11, 2016 |
SYSTEMS AND METHODS FOR UPLINK SIGNALING USING TIME-FREQUENCY
RESOURCES
Abstract
Methods, base stations and access terminals for uplink signaling
are provided. Resource request channel characteristics such as
location in time-frequency, sequence, time slot, are assigned to
each access terminal to distinguish their resource requests from
the resource requests of other access terminals. Access terminals
make requests using a resource request on a resource request
channel having the assigned characteristics. The base station can
then determine which access terminal transmitted the resource
request based on the resource request channel characteristics of
the resource request channel upon which the resource request was
received. The base station then transmits a response to the request
which may for example be a new resource allocation, a default
allocation or a renewal of a previous allocation.
Inventors: |
NOVAK; Robert; (Stittsville,
CA) ; FONG; Mo-Han; (Ottawa, CA) ; VRZIC;
Sophie; (Nepean, CA) ; YUAN; Jun; (Ottawa,
CA) ; YU; Dong-Sheng; (Ottawa, CA) ; MA;
Jianglei; (Kanata, CA) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
Apple Inc. |
Cupertino |
CA |
US |
|
|
Family ID: |
40451521 |
Appl. No.: |
14/887244 |
Filed: |
October 19, 2015 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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12677438 |
Nov 12, 2010 |
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PCT/CA2008/001608 |
Sep 11, 2008 |
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14887244 |
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60971608 |
Sep 12, 2007 |
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61046596 |
Apr 21, 2008 |
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61050303 |
May 5, 2008 |
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61094159 |
Sep 4, 2008 |
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Current U.S.
Class: |
370/330 |
Current CPC
Class: |
H04W 72/0413 20130101;
H04L 5/0055 20130101; H04W 72/04 20130101; H04L 5/0007 20130101;
H04W 52/365 20130101; H04L 1/1812 20130101 |
International
Class: |
H04W 72/04 20060101
H04W072/04; H04L 5/00 20060101 H04L005/00 |
Claims
1. A method for uplink signaling between a base station and an
access terminal of a plurality of access terminals, the method
comprising: by the base station: assigning resources for a resource
request to the access terminal, the assigned resources comprising
periodic time-frequency resources of an orthogonal frequency
division multiplexing (OFDM) based signaling scheme; and receiving
the resource request combined with acknowledge (ACK) and/or
negative acknowledge (NACK) feedback from the access terminal,
wherein the resource request is spread over a plurality of
subcarriers in one or more OFDM symbols of the assigned resources
using at least one orthogonal spreading sequence.
2. The method of claim 1, wherein the periodic time-frequency
resources comprise localized or distributed time-frequency
resources in a plurality of OFDM symbols and a plurality of sub
carriers.
3. The method of claim 1, wherein the resource request comprises an
indicator or a flag.
4. The method of claim 3, wherein the resource request comprises a
request for uplink resources for the access terminal.
5. The method of claim 1, further comprising the base station
identifying the access terminal from which the resource request is
transmitted based at least in part on the resources on which the
resource request is received.
6. The method of claim 1, wherein the resources for the resource
request assigned to the access terminal comprise resources overlaid
on time-frequency resources used for uplink control signaling.
7. The method of claim 1, wherein the resources for the resource
request assigned to the access terminal comprise time-frequency
resources assigned at least in part to a second access terminal of
the plurality of access terminals, the second access terminal using
at least one orthogonal spreading sequence that differs from the at
least one orthogonal spreading sequence used by the access
terminal.
8. A base station configured to receive uplink signaling from an
access terminal of a plurality of access terminals, the base
station comprising: wireless circuitry for performing wireless
communication with the plurality of access terminals; processing
circuitry in communication with the wireless circuitry, wherein the
processing circuitry is configured to cause the base station to:
assign resources for a resource request to the access terminal, the
assigned resources comprising periodic time-frequency resources of
an orthogonal frequency division multiplexing (OFDM) based
signaling scheme; and receive the resource request combined with
acknowledge (ACK) and/or negative acknowledge (NACK) feedback from
the access terminal, wherein the resource request is spread over a
plurality of subcarriers in one or more OFDM symbols of the
assigned resources using at least one orthogonal spreading
sequence.
9. The base station of claim 8, wherein the periodic time-frequency
resources comprise localized or distributed time-frequency
resources in a plurality of OFDM symbols and a plurality of
subcarriers.
10. The base station of claim 8, wherein the resource request
comprises an indicator or a flag.
11. The base station of claim 10, wherein the resource request
comprises a request for uplink resources for the access
terminal.
12. The base station of claim 8, wherein the processing circuitry
is further configured to cause the base station to identify the
access terminal from which the resource request is transmitted
based at least in part on the resources on which the resource
request is received.
13. The base station of claim 8, wherein the resources for the
resource request assigned to the access terminal comprise resources
overlaid on time-frequency resources used for uplink control
signaling.
14. The base station of claim 8, wherein the resources for the
resource request assigned to the access terminal comprise
time-frequency resources assigned at least in part to a second
access terminal of the plurality of access terminals, the second
access terminal using at least one orthogonal spreading sequence
that differs from the at least one orthogonal spreading sequence
used by the access terminal.
15. A non-transitory computer-readable medium storing instructions
that, when executed by processing circuitry of a base station, case
the base station to: assign resources for a resource request to the
access terminal, the assigned resources comprising periodic
time-frequency resources of an orthogonal frequency division
multiplexing (OFDM) based signaling scheme; and receive the
resource request combined with acknowledge (ACK) and/or negative
acknowledge (NACK) feedback from the access terminal, wherein the
resource request is spread over a plurality of subcarriers in one
or more OFDM symbols of the assigned resources using at least one
orthogonal spreading sequence.
16. The non-transitory computer-readable medium of claim 15,
wherein the periodic time-frequency resources comprise localized or
distributed time-frequency resources in a plurality of OFDM symbols
and a plurality of subcarriers.
17. The non-transitory computer-readable medium of claim 15,
wherein the resource request comprises an indicator or a flag that
indicates a request for uplink resources for the access
terminal.
18. The non-transitory computer-readable medium of claim 15,
wherein execution of the instructions by processing circuitry
further cause the base station to identify the access terminal from
which the resource request is transmitted based at least in part on
the resources on which the resource request is received.
19. The non-transitory computer-readable medium of claim 15,
wherein the resources for the resource request assigned to the
access terminal comprise resources overlaid on time-frequency
resources used for uplink control signaling.
20. The non-transitory computer-readable medium of claim 15,
wherein the resources for the resource request assigned to the
access terminal comprise time-frequency resources assigned at least
in part to a second access terminal of the plurality of access
terminals, the second access terminal using at least one orthogonal
spreading sequence that differs from the at least one orthogonal
spreading sequence used by the access terminal.
Description
CROSS-REFERENCE TO RELATED APPLICATIONS
[0001] This application is a continuation of U.S. patent
application Ser. No. 12/677,438 filed Nov. 12, 2010, which is a
National Phase Entry of International PCT Application No.
PCT/CA2008/001608 filed Sep. 11, 2008, which claims the benefit of
U.S. Provisional Application No. 60/971,608 filed Sep. 12, 2007,
U.S. Provisional Application No. 61/046,596 filed Apr. 21, 2008,
U.S. Provisional Application No. 61/050,303 filed May 5, 2008, and
U.S. Provisional Application No. 61/094,159 filed Sep. 4, 2008, all
of which are incorporated by reference herein in their entireties
for all purposes.
FIELD OF THE INVENTION
[0002] The invention relates to wireless communication, and more
specifically to methods and systems for requesting uplink
signaling.
BACKGROUND OF THE INVENTION
[0003] Uplink (UL) signaling generally refers to transmissions from
an access terminal to a base station in a wireless system. Uplink
signaling can require significant resources, and may include
several component messages such as ACK (acknowledgement)/NAK
(negative acknowledgement), CQI (channel quality indicator)
feedback in respect of the channel, MIMO (multiple input, multiple
output) configuration, pilot channel, and resource requests to name
a few specific examples.
[0004] Uplink signaling is used for many different applications.
Some services may be less delay sensitive, for example FTP (file
transfer protocol), HTTP (hypertext transfer protocol), and other
services may be more delay sensitive. Examples of some delay
sensitive services include VoIP (Voice over internet protocol),
video telephony, near-real time video, and gaming.
[0005] In addition, some services have other challenges such as a
limited bandwidth and power for signaling, frequent transmissions
of delay sensitive traffic, a requirement for signaling per packet
or and per transmission, large number of mobile stations, variable
packet sizes, a requirement for adaptive MCS (modulation and coding
schemes) for variable size packets, and a requirement for adaptive
resource scheduling.
[0006] Some existing solutions have incurred a lot of overhead or
delay, and have not been able to accommodate a large number of
mobile stations efficiently.
[0007] In Draft IEEE 802.16m System Description Document, IEEE
802.16m-08/003r1, dated Apr. 15, 2008, it is stated that: [0008]
This [802.16m] standard amends the IEFF 802.16 WirelessMAN-OFDMA
specification to provide an advanced air interface for operation in
licensed bands. It meets the cellular layer requirements of
IMT-Advanced next generation mobile networks. This amendment
provides continuing support for legacy WirelessMAN-OFDMA equipment.
[0009] The standard will address the following purpose: [0010] i.
The purpose of this standard is to provide performance improvements
necessary to support future advanced services and applications,
such as those described by the ITU in Report ITU-R M.2072.
[0011] FIGS. 7-13 of the present application correspond to FIGS.
1-7 of IEEE 802.16m-08/003r1. The description of these figures in
IEEE 802.16m-08/003r1 is incorporated herein by reference.
SUMMARY
[0012] Various approaches to sending a resource request are
provided. These include: [0013] the persistent assignment of
channel resources for transmission of the resource requests--this
can be an entirely new allocation, or can be an allocation of some
or all of a set of existing signaling opportunities for resource
request transmission purposes; [0014] the superposition of resource
requests over other traffic in which case interference cancellation
techniques may be used at the base station to remove interference
due to the superimposed resource request message; [0015] the
superposition of resource requests over other signaling in which
case again interference cancellation techniques may be used at the
base station to remove interference due to the superimposed
resource request message.
[0016] A broad aspect provides a method, for execution by a base
station or other access network component or components, the method
comprising: [0017] assigning a respective set of at least one
resource request channel characteristics to each of a plurality of
access terminals for each access terminal to use to request uplink
transmission resources, each set of at least one resource request
channel characteristics being distinct from each other set of at
least one resource request channel characteristics; [0018]
receiving a resource request on a resource request channel; [0019]
determining which access terminal transmitted the resource request
based on at least one resource request channel characteristic of
the resource request channel upon which the resource request was
received; [0020] transmitting a response to the request.
[0021] A second broad aspect provides a method in an access
terminal, the method comprising: [0022] receiving an assignment of
a set of at least one resource request channel characteristic, the
set of at least one resource request channel characteristic being
distinct from each other set of at least one resource request
channel characteristics assigned to another access terminal; [0023]
transmitting a resource request on a resource request channel
having the set of at least one resource request channel
characteristic, the set of at least one resource request channel
characteristic identifying the access terminal as a source of the
request; [0024] receiving a response to the request.
BRIEF DESCRIPTION OF THE DRAWINGS
[0025] Embodiments of the present application will now be
described, by way of example only, with reference to the
accompanying drawing figures, wherein:
[0026] FIG. 1 is a block diagram of a cellular communication
system;
[0027] FIG. 2 is a block diagram of an example base station that
might be used to implement some embodiments of the present
application;
[0028] FIG. 3 is a block diagram of an example wireless terminal
that might be used to implement some embodiments of the present
application;
[0029] FIG. 4 is a block diagram of an example relay station that
might be used to implement some embodiments of the present
application;
[0030] FIG. 5 is a block diagram of a logical breakdown of an
example OFDM transmitter architecture that might be used to
implement some embodiments of the present application;
[0031] FIG. 6 is a block diagram of a logical breakdown of an
example OFDM receiver architecture that might be used to implement
some embodiments of the present application;
[0032] FIG. 7 is FIG. 1 of IEEE 802.16m-08/003r1, an example of
overall network architecture;
[0033] FIG. 8 is FIG. 2 of IEEE 802.16m-08/003r1, a relay station
in overall network architecture;
[0034] FIG. 9 is FIG. 3 of IEEE 802.16m-08/003r1, a system
reference model;
[0035] FIG. 10 is FIG. 4 of IEEE 802.16m-08/003r1, the IEEE 802.16m
protocol structure;
[0036] FIG. 11 is FIG. 5 of IEEE 802.16m-08/003r1, the IEEE 802.16m
MS/BS data plane processing flow;
[0037] FIG. 12 is FIG. 6 of IEEE 802.16m-08/003r1, the IEEE 802.16m
MS/BS control plane processing flow;
[0038] FIG. 13 is FIG. 7 of IEEE 802.16m-08/003r1, generic protocol
architecture to support multicarrier system;
[0039] FIG. 14 is an example of a distributed resource for resource
request;
[0040] FIG. 15 is an example, of a localized resource for resource
request;
[0041] FIG. 16 is an example of an access terminal access and
resource allocation flow;
[0042] FIG. 17 is a graphical depiction of an initial access
channel;
[0043] FIG. 18 is a graphical depiction of an access channel used
for initial access and resource request;
[0044] FIG. 19 is another graphical depiction of an access channel
used for initial access and resource request;
[0045] FIG. 20 is another graphical depiction of an access channel
used for initial access and resource request; and
[0046] FIG. 21 is a graphical depiction of a tile that is divided
into two sections for the purpose of uplink signaling.
DETAILED DESCRIPTION
[0047] Various methods are provided to signal a request for a
resource assignment for an UL (uplink) transmission by an access
terminal. An access terminal is any device that is used to access a
wireless network. Access terminals may be mobile stations or fixed
wireless terminal for example. Throughout this description, such a
request is referred to as a "resource request". It is to be
understood that this refers generally to a request to be granted an
opportunity to make an uplink transmission or transmissions. It is
noted that the signaling or other traffic may use a number of
transmission methods including but not limited to: [0048]
Orthogonal frequency division multiplexing (OFDM) based schemes;
[0049] OFDM with subcarrier-hopping sequences; and [0050] Code
division separation CDMA based or combinations thereof.
[0051] In some implementations the physical resource used comprises
OFDM symbols. In some embodiments, these symbols are organized into
frames that in turn are composed of subframes, each sub-frame
containing a plurality of symbols. In some embodiments, a plurality
of frames compose a superframe.
[0052] In some embodiments the unit of resource allocation for
uplink transmission is a RB (resource block). The physical
structure of a resource depends on the system implementation. In
some embodiments, on the uplink each resource block is defined as a
physically contiguous tile in an OFDM time-frequency space. In
other embodiments, on the uplink each resource block is defined as
a distributed set of resource tiles.
[0053] Some embodiments involve the assignment of a respective set
of at least one resource request channel characteristics to each of
a plurality of access terminals for each access terminal to use to
request uplink transmission resources, each set of at least one
resource request channel characteristics being distinct from each
other set of at least one resource request channel characteristics.
Access terminals can then make a resource request using the
assigned set of at least one resource request channel
characteristics, and this is used by the base station to determine
who sent the request. Examples of characteristics include an
assigned unique spreading sequence; an assigned unique location in
time-frequency, an assigned time slot. Combinations may also be
used, for example a spreading sequence and location in
time-frequency in which case the spreading sequence alone need not
be unique, and the location in time-frequency need not be unique,
but the combination of the spreading sequence and the location is
distinct from the combination assigned to other access
terminals.
(A) Reserved Segment of Time-Frequency or Time-Frequency-Space for
UL Signaling
[0054] In a first approach, a reserved resource within an uplink
transmission resource having time and frequency dimensions is
employed and dedicated solely to the purpose of uplink signaling.
In some embodiments, the space dimension may be employed for MIMO
(multiple input, multiple output) applications. The size, nature,
frequency of such reserved resource is implementation specific, and
depends upon the nature of the uplink transmission resource.
[0055] An OFDM (orthogonal frequency division multiplexing)
transmission resource is an example of a transmission resource
having time and frequency dimensions. The frequency dimension
consists of a set of sub-carriers, and the time dimension consists
of OFDM symbol durations.
[0056] In some embodiments, the reserved resource is a contiguous
block within the time-frequency OFDM transmission resource.
[0057] In some embodiments, code division separation is used by the
access terminals to distinguish the transmissions of each access
terminal and/or to distinguish a type of signaling being performed.
For example, in some embodiments each access terminal is assigned a
sequence from a set of sequences. Each access terminal transmits
its resource request using its assigned sequence. The base station
that receives the request can determine which access terminal
transmitted the request by determining which sequence was used. In
some embodiments, the sequences are orthogonal.
Superposition of Resource Request on Traffic and/or Other
Signaling
[0058] In some embodiments, some or all of the transmission
resource used for transmission of the resource requests is the same
as that used for traffic and/or other signaling, typically by a
different access terminal, within a time-frequency transmission
resource space. This is referred to superposition or overlaying of
transmissions. In some embodiments resource requests can be
overlaid over the entire signaling bandwidth. This approach may
provide the advantage of not designating a specific resource set
for signaling. In some embodiments, code division separation UL
signaling can be used with this method. This type of signaling may
be useful for, but not limited to, resource request signaling for
delay sensitive applications.
[0059] In some such embodiments, after a resource request is
detected, it can be removed from the traffic channel over which it
was superimposed through interference cancellation (IC).
(B) Superposition of Resource Request on Traffic and/or Other
Signaling on Persistent Resource
[0060] In some embodiments, superposition of resource requests over
traffic and/or other signaling is performed using a persistent
resource. A persistent resource is a transmission resource that is
known to the access terminal and the base station that occurs
recurringly and as such does not need to be signaled in a detailed
manner each time it is to be used. In some embodiments, the
persistent resource is a periodic resource assigned to a unique
access terminal. In other embodiments, several access terminals may
share a persistent resource assignment in which case some
collisions may occur. In some embodiments, code division separation
UL signaling can be used with this method. This type of signaling
is useful for, but not limited to, resource request signaling for
delay sensitive applications.
[0061] In some such embodiments, after a resource request message
is detected, it can be removed from the traffic channel over which
it was superimposed through interference cancellation (IC).
(C) Superposition of Resource Request on Traffic and/or Other
Signaling on Specific Resource or Set of Resources
[0062] In some embodiments, the superposition of resource requests
on traffic and/or other signaling on a specific resource or set of
resources is employed. In some embodiments, the transmission of the
uplink signaling on a given set of resources indicates the access
terminal is requesting assignment on those resources. In some
embodiments, an access terminal may be identified by a unique
spreading sequence, or set of sequences. In some embodiments, the
UL signaling may be sent only over the "first" resource block of a
desired assignment.
(D) Unique Persistent Resource Assigned to Each Access Terminal or
to a Set of Access Terminals
[0063] In some embodiments, a persistent recurring resource for UL
signaling is assigned to each access terminal. This makes detection
of the resource request signal relatively simple at the base
station, as the base station only need look for a resource request
from the particular access terminal on that access terminal's
assigned resource. With this approach, there is no contention for
the capacity to transmit a resource request. The resource may be
dedicated to resource request transmission, or may overlaid over
traffic and/or signaling as described in methods B and C above.
[0064] In another embodiment, a number of different persistent
recurring resources are assigned, and each of the different
persistent recurring resource is assigned to one or more access
terminals. In this case, there is contention for the capacity to
transmit a resource request, but only with other access terminals
assigned the same persistent recurring resource. In some
embodiments, different spreading codes are assigned to access
terminals that are assigned the same persistent recurring resource.
The resource may be dedicated to resource request transmission, or
may overlaid over traffic and/or signaling as described in methods
B and C above.
[0065] In some embodiments, this approach is used in conjunction
with overlaying the signaling over traffic or other signaling. In a
specific example, the following approach is followed: [0066] If an
access terminal has packet to transmit, it will transmit signaling
using its assigned resource. [0067] The base station will receive
signaling. In response, an assignment is made to the access
terminal for uplink transmission. [0068] The BS may have assigned
some or all of the resource assigned to the access terminal for
resource request signaling to another access terminal in this slot.
In some embodiments, for the purpose of receiving the transmission
of the other access terminal, interference cancellation can be used
to remove the effects of the resource request signaling. [0069] If
the access terminal does not have a packet, it does not transmit
anything using its assigned resource. The resource is left blank,
and no assignment message is sent for that access terminal.
Resource Request Content
[0070] Resource request content refers to what is conveyed by the
resource request. In some embodiments, this may be spread using one
or more spreading sequences as described below.
[0071] In some embodiments, the resource request content is only a
flag or indicator as opposed to a message that might include
additional fields, so that the detection of the flag or indicator
is a request for a predefined response from the base station. In
some embodiments, the predefined response to the detection of an UL
indicator for an access terminal is to assign resources for at one
least HARQ (hybrid automatic repeat request) transmission on the
UL. As a specific example, the indicator may be a request for a
fixed size assignment for VoIP transmission.
[0072] In some embodiments, the resource request contains multiple
fields including one or more of desired resource, CQI, MIMO method,
etc.
[0073] In some embodiments, one or more bits are used to indicate:
signaling resource for transmission of default parameters and size.
For example 1 to 3 bits might be transmitted, each spread using a
spreading sequence. Using a specific set of more than one bit can
improve detection by reducing false alarm probability. Detection is
all that is needed as the sequence(s) are assigned to a specific
access terminal or user, and the transmission of this signaling is
just to indicate that a packet is ready for transmission at the
access terminal. This signaling can be used like a "page" of some
kind.
[0074] In some embodiments, fields such as PF (packet
format)/resource size, CQI with sub-band index (sub-band spans
several resources), CRC might be included in the resource request.
In some embodiments, the fields included may be variable. For
example, a CQI might be included for requests in respect of initial
transmissions, and then omitted for requests for
retransmissions.
[0075] In some embodiments initial resource may be different from
subsequent resource requests. An initial resource request is one at
that initiates a service, or re-configures such as service.
Subsequent requests can be use to renew or maintain such as
service.
[0076] In some embodiments, the UL resource request for an access
terminal is 4-10 bits in size. In some embodiments, the initial
resource request message contains limited fields. In a specific
example, the request includes QoS and 1.sup.st transmission
spectral efficiency/or access terminal buffer size including CRC.
This can be reliably signaled through the use of diversity.
[0077] In some embodiments, the resource request is combined with
other messages to include other feedback, for example ACK/NAK
feedback.
[0078] In some embodiments with persistent resource for UL
signaling, traffic intended for the access terminal may also use
the persistent resource for one or more HARQ transmission.
[0079] In some embodiments, several different uplink messages may
be multiplexed using a combination of the described methods and
procedures.
[0080] In some embodiments, the resource request is an indication
to the base station that an access terminal requires UL resource(s)
on which transmit.
[0081] In some embodiments, the resource request is an indication
to the base station that an access terminal requires the use of a
UL resource(s) previously assigned to it.
[0082] The methods for uplink signaling have been described in the
context of transmitting resource requests. In other embodiments,
one or more of these approaches is used by the access terminal to
indicate to the base station one or more parameters associated with
an UL assignment or UL assignment scheduling.
[0083] More generally still, the embodiments described thus far
have focused on providing mechanisms for transmitting resource
requests, although as indicated above, these mechanisms may also be
used for other types of uplink signaling.
[0084] In some embodiments access terminals perform signaling for
one or more of initial access to a system, resource request, to
trigger renewal of negotiated service, and to propose an allocation
re-configuration.
[0085] Details on the designs for each type signaling. In addition,
an access and resource allocation flow is described. Several
signaling structures and channels are described herein. One or more
of these structures and channels can be used together, or
separately.
[0086] In some embodiments, an assignment message transmitted on
the downlink to the access terminal containing a resource
allocation is also used as a confirmation that the resource request
was received. Upon receipt, the access terminal begins UL
transmission using the assigned resource, be it a newly assigned
resource, or a persistent resource.
[0087] In some embodiments, the resource request is spread by a
spreading sequence. The spreading may be in time, frequency or both
time/frequency. For example, the signaling may be spread over a set
of subcarriers in one or several OFDM symbols. FIG. 14 shows an
example of code division spreading for OFDM transmissions using a
distributed resource within an available time-frequency OFDM
resource. FIG. 15 shows an example of code division spreading for
OFDM transmissions using a contiguous resource. In some embodiment,
orthogonal spreading sequences may be used. In other embodiments,
non-orthogonal spreading sequences are used.
[0088] For example, a spreading length 128 might be employed, but
other lengths are possible.
[0089] In some embodiments, direct sequence CDMA may also be
used.
[0090] In some embodiments, each access terminal is assigned a
respective set of sequences to use.
[0091] In some other embodiments, all access terminals are assigned
the same set of sequences to facilitate detection at the base
station.
[0092] In some embodiments, orthogonal sequences such as Zadoff-Chu
or Walsh sequences may be used.
[0093] In some embodiments, the sequence length is less than the
capacity of a RB. If N RB's are assigned for each resource request
channel, the sequence may be repeated over all RB's.
[0094] In some other embodiments, the sequence may be spread over
all N RB's.
[0095] In some embodiments, signaling can be configured per
transmission, per packet, or per multiple packets or with defined
combinations of these granularities. In some cases, relatively
frequent signaling may reduce some packet delay. Per transmission
signaling allow for frequent scheduling of re-transmissions. The
reliability of signaling may be reduced if it is per
transmission.
[0096] In some embodiments, the resources for UL signaling are
shared by a set or all access terminals. in some embodiments, the
resources for UL signaling may be a large portion or all of the
resources.
Selecting Between Transmission Resources
[0097] In some embodiments, the access terminal has the capability
of selecting between several different persistent resources to
transmit its resource request. In some such embodiments, the access
terminal selects the persistent resource that has been idle the
longest. This may have the effect of reducing the collisions.
Access Terminal Access and UL Resource Allocation Flow
Example--FIG. 16
[0098] Referring now to FIG. 16, shown is an example of an access
terminal access and UL resource allocation flow. Shown is
functionality for initial access, generally indicated at 200, and
functionality for resource allocation, generally indicated at 202.
An overview of FIG. 16 will be provided first, followed by detailed
example implementations for several of the steps. Note that various
embodiments may include an arbitrary subset of the
steps/functionality shown in FIG. 16.
[0099] Initial access 200 begins with an access request in block
204 using a random access channel. The access terminal signals on a
contention based resource using a randomly selected sequence from a
set of sequences. The base station responds with an access grant in
block 206. This can include for example an initial DL/UL access
grant, MAC (medium access control) ID, etc. Grant ID is based on
access signaling. The "access grant" from the BS is a message sent
to the access terminal. In some embodiments, the message is sent
with a Grant ID to target the access terminal. As the access
terminal may not been identified except to send a "randomly
selected sequence", the grant ID in this case can be based in some
way the "randomly selected sequence", or access signaling.
[0100] In some embodiments, in block 208, using the initial UL
assignment, the access terminal signals access details such as MAC
ID, if already assigned. At that point, the access terminal has
successfully accessed the system. In some embodiments as part of
block 208, a re-configuration header is embedded in the first
uplink packet transmission, i.e., the packet transmitted using the
initial UL assignment, to specify details of a resource request,
such as further specifications about the assignment, MIMO mode,
backlog of buffer at the access terminal, etc.
[0101] Resource allocation 202 begins with a UL resource request at
block 210. The access terminal signals an initial resource request
that may for example be to start a service. This may for example be
performed using a scheduled or non-scheduled resource. The base
station responds at block 212 with a UL resource assignment. This
may include a DL access grant, etc., and UL assignment for service
specification. As indicated below, the access terminal may specify
or re-configure the service within the allocation using a MAC
header. Next, the access terminal begins UL data transmission 214
using the UL resource thus assigned. In some embodiments, the
access terminal then has the option of signaling a re-configuration
of the service. This may, for example, be signaled as part of a MAC
header of a packet sent using the existing allocation. In some
embodiments, the MAC header may be sent alone. In some embodiments,
the resource allocation protocol allows the access terminal to
signal a renewal of the service. This may, for example, be signaled
as part of a MAC header of a packet sent using the existing
allocation or a MAC header sent alone. In response, as part of
block 212, further UL resource assignment may be transmitted to the
access terminal. At block 216, the access terminal transmits a UL
service renewal. This is sent using an access terminal/service
specific ID. In response, as part of block 212, a further UL
resource assignment may be transmitted to the access terminal. The
response is a UL assignment consistent with configuration
negotiated before (persistent resource, MIMO mode, size of
resource, etc.)]
[0102] Details of example implementation of several of the blocks
shown in FIG. 16 will now be described.
Access Request 204
[0103] As indicated above, the process begins when the access
terminal attempts to access the system. At this point in common
cases, the access terminal has already synchronized with a serving
sector. A random access (RA) channel is used for an access terminal
to initially access the system. Access to the system may provide
the access terminal with an Access terminal ID (such as a MAC ID),
and allow the access terminal to receive resource allocations (UL
and/or DL) from the base station. The physical structure of the
random access channel is implementation specific. Three specific
options, each of which will be described in further detail below,
include: [0104] Option 1: random access channel uses a designated
resource; [0105] Option 2: random access channel is overlaid on UL
control resource (superposition with UL control); [0106] Option 3:
random access channel is overlaid on wideband UL resources
(superposition with traffic, etc). A common aspect of these options
is that the access terminal randomly selects an access channel
signaling ID (identifier). The nature of the available signaling
IDs is implementation specific. It may for example be a specific
spreading sequence, time-frequency location, time slot, interlace,
etc. Specific examples are provided below. The set of signaling ID
options are known to base stations and access terminals. An index
may be associated with each signaling ID option that is also known
to the base stations and access terminals.
[0107] In some embodiments, in response to a random access channel
signal, the base station transmits an assignment message that
assigns one or more of the following: [0108] an access terminal ID
to the access terminal; [0109] an initial UL resource for the
access terminal to provide further information such as access
terminal equipment capabilities, etc.; [0110] a possible DL
resource assignment requesting information from the access
terminal, and additional details (group assignment, base station
procedures, etc).
[0111] In addition, in some embodiments, the assignment message
sent to the access terminal from the base station identifies the
base station based on the randomly selected signaling ID option
selected by the access terminal for random access. For example, in
some cases the control channels are normally generally scrambled in
some manner by a sequence associated with the access terminal ID.
In some embodiments, in response to a random access signaling (for
example during initial access to the system), the base station will
send a control message scrambled by a sequence associated with the
randomly selected signaling ID instead of the access terminal ID.
In some embodiments, the randomly selected signaling ID is an ID
specifying one or more parameters such as sequence index, sequence
location, etc.
[0112] In some embodiments, a subset of the defined signaling ID's
are reserved for access terminals that have already been assigned
access terminal ID's. An example of such an access terminal is an
access terminal that is in hand-off, and is attempting to access a
new serving sector. In this case, an access terminal access
terminal randomly selects from a first subset of a defined set of
random access signaling IDs if it does not yet have an assigned
access terminal ID, and a different subset of the defined set of
random access signaling IDs if it does have an access terminal
ID.
Option 1--Dedicated Resource for UL Access Channel
[0113] The first above-referenced option for the UL random access
channel involves use of a designated resource allocated for these
access requests. A contention based channel for multiple access
terminals to request access is employed. The access request is
spread and/or repeated across a resource allocated exclusively for
initial access. In some embodiments, the resource is allocated for
initial access or resource requests. Specific examples are provided
below. In the event the resource allocated for the random access
channel includes multiple different transmission location
possibilities (for example multiple locations in an OFDM
time-frequency resource), the access terminal randomly selects a
location of the multiple different location possibilities.
[0114] In some embodiments, the access terminal randomly selects a
sequence from a set of L sequences known to both the access
terminal and the base station.
[0115] In some embodiments, the sequence length is selected so as
to span N RB's, where N>1.
[0116] In some other embodiments, the sequence length is chosen to
confine a full sequence to be transmittable using a single RB. For
embodiments in which a RB is a contiguous block, and in which the
sequences are orthogonal to begin with, by confining spreading
sequence transmission to one RB, the spreading sequences maintain
substantial orthogonality as a contiguous RB is typically virtually
frequency flat.
[0117] In some embodiments, the sequences are repeated in each of a
plurality RB to gain diversity.
[0118] If many resources are assigned for the random access, the
resources may be divided into M time-frequency blocks for random
access. In such an embodiment, the number of distinct
codes+resource combinations per subframe is L.times.M. In some
embodiments, the value of M can be dynamically specified by the
BS.
[0119] In some embodiments, a subframe within a frame or superframe
(or otherwise specified set of F frames) for an access request is
also randomly selected. In this case, the number of distinct
codes+resource+subframes per superframe is L.times.M.times.F.
[0120] In some embodiments, the L sequences are an orthogonal set
of spreading sequences.
[0121] In some embodiments, the L sequences are divided into two
groups so as to allow sequence selection to make two types of
indications: [0122] 1) system access request from an access
terminal without previously assigned access terminal ID; [0123] 2)
system access request from an access terminal with previously
assigned access terminal ID.
[0124] When an access grant is transmitted in response to such a
request, in some embodiments the DL control segment access grant is
scrambled by a sequence associated with the randomly selected
access ID (e.g., sequence/resource block ID).
[0125] An example of this approach is depicted in FIG. 17. Here,
the available resource is an OFDM time-frequency resource.
Frequency is on the vertical axis, and time is on the horizontal
axis. Each box in FIG. 17, also referred to as a "tile", represents
a contiguous set of sub-carriers over a number of OFDM symbols
forming a subframe. Note that the entire vertical axis is not
shown; it is assumed that there is a set of N.times.M tiles in the
vertical direction available for use as access channels, where M is
the number of initial access locations per sub-frame, and N is the
number of tiles per initial access location. In the illustrated
example, N=3, but this is implementation specific. For each of the
M initial access locations within a sub-frame, a set of N=3 tiles
is assigned. Thus, for example, the three tiles 240 labeled "A" are
assigned as one initial access location. Other initial access
locations can be assigned for a set of F subframes making up a
frame or superframe. F=4 in the illustrated example, but this is
implementation specific. Within a given access location, any of L
different sequences can be used. Thus, the total number of distinct
codes+resource+subframes permutations that can be accommodated is
given by L.times.M.times.F.
[0126] In some embodiments, the above-described approach is used
for resource requests in addition to, or instead of for requesting
access.
Option 2--UL Access Channel Overlaid with UL Control
[0127] With this option, the UL random access channel is again a
contention based channel for multiple access terminals to request
access. The random access requests are overlaid with resources
allocated to UL control. The request is spread/repeated across the
resources used for Uplink Control (CQI, etc.). The access terminal
randomly selects the location if multiple possibilities are
available.
[0128] In some embodiments, the access terminal randomly selects a
sequence from a set of L sequences known to both the access
terminal and the base station.
[0129] In some embodiments, the sequence length is selected to
which spans N RB's, where N>1.
[0130] In some other embodiments, the sequence length is chosen to
confine a full sequence to be transmittable using a single RB. For
embodiments in which a RB is a contiguous block, and in which the
sequences are orthogonal to begin with, by confining spreading
sequence transmission to one RB, the spreading sequences maintain
substantial orthogonality as a contiguous RB is typically virtually
frequency flat.
[0131] In some embodiments, the sequences are repeated in each of a
plurality RB to gain diversity.
[0132] If many resources are assigned for uplink control, the
resources may be divided into M time-frequency blocks for random
access. In such an embodiment, the number of distinct
codes+resource combinations per subframe is L.times.M. In some
embodiments, the value of M can be dynamically specified by the
BS.
[0133] In some embodiments, the subframe within the frame or
superframe (or otherwise specified set of F frames) for an access
request is also randomly selected. In this case, the number of
distinct codes+resource+superframes per subframe is
L.times.M.times.F.
[0134] In some embodiments, the L sequences are an orthogonal set
of spreading sequences.
[0135] In some embodiments, the L sequences are divided into two
types of indications: [0136] 1) system access request from an
access terminal without previously assigned access terminal ID;
[0137] 2) system access request from an access terminal with
previously assigned access terminal ID.
[0138] When an access grant is transmitted in response to such a
request, the DL control segment access grant is scrambled by a
sequence associated with the sequence used to generate the resource
request and/or the location of the frequency request in terms of
time-frequency location and/or subframe so as to associate the
response with the request.
[0139] The base station can attempt interference cancellation to
remove the RA channel from UL control.
[0140] In some embodiments, the above-describe approach is used for
resource requests in addition to, or instead of for requesting
access.
Option 3--UL Random Access Channel Overlaid Over Wideband UL
Resource
[0141] With this option, UL random access channel is a contention
based channel for multiple access terminals to request access that
employs a resource that is overlaid over the UL resources available
for control and traffic. The request is spread/repeated across a
portion of the UL channel, possible the entire bandwidth. The
access terminal randomly selects the location if multiple
possibilities are available.
[0142] For this embodiment, random access operation for all access
terminals is assigned one length L sequence, and location if
multiple possibilities are available.
[0143] In some embodiments, the total available resources blocks,
N.sub.T, may be divided into M time-frequency blocks for random
access each defining a respective location for an access sequence.
The access sequence spans (through spreading and repetition)
N.sub.T/M=N RBs (e.g., N=3).
[0144] In this case, the number of possible distinct requests per
subframe is M. The access terminal randomly selects one of the M
possibilities.
[0145] In some embodiments, the subframe within a frame or
superframe for the request is also randomly selected by the access
terminal.
[0146] In some embodiments, the sequences for random access are an
orthogonal set of spreading sequences.
[0147] In some embodiments, two sequences are defined for two types
of indications: [0148] 1) system access request from an access
terminal without previously assigned access terminal ID; [0149] 2)
system access request from an access terminal with previously
assigned access terminal ID.
[0150] When an access grant is transmitted in response to such a
request, the DL control segment access grant is scrambled by a
sequence associated with the location and sequence used so as to
uniquely associate the response with the resource request, and
effectively identify the access terminal.
[0151] In some embodiments, the base station can attempt
interference cancellation to remove the RA channel from UL
control.
[0152] In some embodiments, as an alternative to, or in addition to
using interference cancellation, the base station may try decoding
UL control and traffic transmissions with two possibilities: with
and without the assumption that a random access request was
sent.
[0153] In some embodiments, the above-described approach is used
for resource requests in addition to, or instead of for requesting
access.
Access Grant/Initial Assignment 206
[0154] If the access terminal has sent a signaling option that
indicates it does not have an access terminal ID, then in response
to the initial access request, the base station sends a control
message containing an access terminal ID scrambled by a sequence
associated with the random access signal ID.
[0155] If the access terminal has sent a signaling option
indicating it does have an access terminal ID, then the base
station sends a control message scrambled by a sequence associated
with the random access signaling ID, and the response need not
contain an access terminal ID. In this case, the access terminal
indicates its access terminal ID in the next UL transmission
containing details such as access terminal equipment capabilities,
etc.
Resource Request 214
[0156] Once an access terminal has accessed the system, when the
access terminal has information to transmit to the base station,
the access terminal needs to request resources on the UL to do so.
The specifics of this are implementation specific. Several specific
options each of which will be described in detail below include:
[0157] Option 1: use UL control resource; [0158] Option 2: use
random access channel with scrambling sequence; [0159] Option 3:
overlay request on wideband resources; optionally CRC protected.
Option 1--UL Resource requests Use UL Control Resource
[0160] With this option, resource requests are made using dedicated
resources within resources allocated to control. Note this is
distinct from overlaying the request over the control resource;
rather, part of the control resource is used for resource requests
rather than other types of control signaling. In some embodiments,
the control resource is formed of a set of UL control tiles, a
control tile being a contiguous block of time-frequency space
allocated for control signaling. In some embodiments, the presence
of a resource request is specified by an UL control message
type.
[0161] In some embodiments, the dedicated UL control resources are
specified persistently for each access terminal. In some
embodiments, the amount of resource allocated to an access terminal
in this manner is different for different frames according to a
pre-determined pattern. The sizes are known at the access terminal
and base station and do not need to be signaled after
configuration.
[0162] In some embodiments, the resource request may occupy a field
nominally provisioned for some other message, for example CQI,
ACK/NAK, precoder index, etc. The presence of a request may be
specified by the UL control message type. In order to transmit the
resource request, the access terminal sets the UL control message
type to a message configuration that includes space for a resource
assignment. Therefore, the size of the message does not necessarily
need to be changed from the specified size for that subframe. With
this approach, the presence of the resource request field is
dynamic, but does not affect the pre-determined size of the access
terminal's UL control resource.
[0163] In some embodiments, the resource request is encoded with
other UL control data for the access terminal so that resource
request can be reliably received.
[0164] In some embodiments, the resource request is a single
"on/off" indication. In this case, details of the assignment can be
given in a re-configuration message, or known from previous or
default configurations.
[0165] In some embodiments, the resource request is a message. Some
details of the assignment such as delay constraints, QoS, packet
backlog, resource size, etc. can be indicated in the resource
request. Further details of assignment can be given in a
re-configuration message, or known from previous or default
configurations.
[0166] In some embodiments, both the on/off indication and the more
detailed resource request message approaches are possible using two
different types of resource request message, with a control message
type being specified dynamically.
[0167] In some embodiments, the UL control resource can be
specified by a secondary broadcast channel. In some embodiments, UL
resources can be allocated across distributed RB's blocks.
[0168] In some embodiments, a resource request is 4-10 bits
indicating QoS and 1.sup.st transmission spectral efficiency/or
access terminal buffer size.
Option 2--Resource Requests Use Random Access Channel with
Scrambling Sequence
[0169] Details of an example access channel design in which access
channel sequences/locations are used for define a set of random
access signaling IDs have been described above. With this
embodiment, a similar approach is used for the purpose of resource
requests. In some embodiments, the approach is used both for
initial access and resource requests. The UL resource request uses
a contention based channel for multiple access terminals to request
UL transmission resources. After system access, an access terminal
is assigned one of a set of random access signaling IDs (i.e.,
channel sequences/location). Resource requests are then transmitted
using this sequence/channel configuration.
[0170] In some embodiments, access terminals may also be assigned
specific subframes for resource request opportunities. The presence
of signaling in the assigned resource is a unique identifier for an
access terminal's resource request.
[0171] In some embodiments, a set of signaling ID's are reserved
for resource requests that cannot be used for initial access. The
assigned sequence/location is a unique identifier for an access
terminal's resource request. Each access terminal is assigned one
signaling ID to identify signaling as resource request signaling of
a particular access terminal.
[0172] In some embodiments, each access terminal is assigned one
signaling ID from a full set of signaling ID's. In some
embodiments, the sequence is scrambled by a resource request
specific scrambling sequence to identify the request as a resource
request as opposed to a request for initial access. In this case,
the assigned sequence/location/scrambling is a unique identifier
for a particular access terminal's resource request.
[0173] In some embodiments, an access terminal may be assigned
multiple signaling ID's for different configured services. For
example, an access terminal might be assigned one for VoIP resource
requests, one for http traffic resource requests, etc.
[0174] In some embodiments in which option 2 is available, if a
given access terminal has another mechanism for resource request
(e.g., option 1 described above), and opportunities for requests
are frequent the mobile device may not be necessarily assigned
signaling for transmitting resource requests in using option 2.
[0175] An example of the approach introduced above in which a set
of access channel locations is divided between initial access and
resource request utilization will be described with reference to
FIG. 18. Shown is a set of access channel locations within a single
subframe. The layout is similar to that described previously with
reference to FIG. 17. There is a set of M access channels having
associated access channel IDs "ACH Signal ID 0", . . . , "ACH
Signal ID M-1". Note that the example depicts only a single
resource block per access channel, but alternatively multiple
resource blocks per access channel maybe defined as in the example
of FIG. 17. The access channel locations are divided into two
types. The top n.sub.ACH locations, generally indicated at 250, are
assigned for initial access use. The bottom M-n.sub.ACH locations,
generally indicated at 252, are assigned for resource request use.
In some embodiments, the division of the available locations
between initial access and resource requests, as defined by the
parameter n.sub.ACH, is signaled, for example as part of superframe
information. In this manner, it can be made configurable based on
traffic conditions. As in other embodiments described herein,
multiple signaling resources can be assigned to the same access
terminal for multiple service requests.
[0176] An example of the approach introduced above in which a set
of access channel locations is not divided between initial access
and resource request utilization, and in which scrambling is used
to separate access requests from resource requests will be
described with reference to FIG. 19. Shown is a set of access
channel locations within a single subframe. The layout is similar
to that described previously with reference to FIG. 17. There is a
set of M access channel channels having associated access channel
IDs "ACH Signal ID 0", . . . , "ACH Signal ID M-1". Note that the
example depicts only a single resource block per access channel,
but alternatively multiple resource blocks per access channel maybe
defined as in the example of FIG. 17.
[0177] For the embodiment of FIG. 19, an initial access request
specific sequence is employed for access requests. Such a request
can be made using any of the M available locations in a subframe
that is randomly selected by an access terminal that needs to make
an access request. For example, the access channel location 260
having "ACH Signal ID 1" might be randomly selected by an access
terminal to make an initial access request. In some embodiments,
multiple specific sequences are used to specify whether the request
is handoff or initial access.
[0178] For the embodiment of FIG. 19, a resource request specific
sequence is employed for access requests. Each access terminal is
assigned a specific location for the purpose of making resource
requests. In the illustrated example, access channel location 262
having ACH Signal ID n.sub.MS1 has been assigned to a first access
terminal, and access channel location 264 having ACH Signal ID
n.sub.MS2 has been assigned to a second access terminal. A given
access channel location will only contain a resource request if the
specific access terminal assigned to the location has transmitted a
resource request.
[0179] In yet another example in which the random access channel is
used for both initial access and resource requests, the available
different signaling IDs are each assigned to one of a plurality of
request types. A specific example of such a set of request types
includes: [0180] Initial access; [0181] Initial access with already
assigned access terminal ID (i.e., handoff); [0182] Resource
request type 1: basic; [0183] Resource request type 2: renewal of
service; [0184] Resource request type 3: predefined
configuration.
[0185] An example of this is depicted in FIG. 20 in which: [0186]
Access channel locations identified as ACH Signal ID 0, . . . , ACH
Signal ID n.sub.1-1 are assigned to request type 1, as generally
indicated at 270; [0187] Access channel locations identified as ACH
Signal ID n.sub.1, . . . , ACH Signal ID n.sub.2-1 are assigned to
request type 2, as generally indicated at 272; [0188] and so
on.
[0189] In some embodiments, the division of the signaling IDs
between the various indications may be configurable by the base
station, for example based on traffic.
[0190] As in other embodiments described herein, multiple signaling
resources can be assigned to the same access terminal for multiple
service requests.
Option 3--UL Resource Request Overlaid Request on all UL
Resources
[0191] With this embodiment, the UL resource request uses resources
specified persistently. These may include one or multiple RB's.
Multiple RB's may be distributed to provide diversity. The UL
resource request is overlaid with other traffic/control on some or
all of the same resources as traffic/control.
[0192] In some embodiments in which Option 3 is available, if a
given access terminal access terminal has another mechanism for
resource request (for example option 1 described above), and
opportunities for requests are frequent enough, it may not
necessarily be assigned signaling for transmitting resource
requests using Option 3.
[0193] In some such embodiments, interference cancellation is used
at the BS to remove the effects of the resource request from other
traffic/control transmissions. The resource requests of different
access terminals are separated by the location of RBs and/or and
subframe, and/or assigned sequences.
UL Data Transmission 210
[0194] In some embodiments, as part of a transmission using an
existing allocation, an access terminal can embed a header on a
packet transmission which can provide details/parameters on
configuration, or reconfiguration on an assignment.
[0195] After an access terminal has been assigned a UL resource,
the assignment can be further configured through additional
message(s) embedded in data packet. In some embodiments, the
parameters for the first transmission are specified in a resource
request, set to default values based on capability negotiation, set
to a previous configuration based on renewal, or set in some other
manner.
[0196] The access terminal can change the assignment parameters by
including additional re-configuration message(s) encoded with data
packets, to take effect at the start of the next packet
transmission. This has the benefit of taking advantage of HARQ for
this control message, assuming of course that HARQ is in place for
the packet transmission.
[0197] In a specific example, a field is appended to a packet prior
to encoding, and a field in the header of the packet is used to
indicate the presence and/or type of service re-configuration
message. After decoding at the base station, the header is examined
to determine if an additional re-configuration message has been
added to the packet with re-configuration information.
[0198] The following is a specific example of header operation:
[0199] 2-bit header field to indicate presence, and type of service
re-configuration message as follows: [0200] `00` no change to
configuration, no re-configuration message; [0201] `01` no change
to configuration, no re-configuration message, extend service for
another packet; [0202] `10` re-configuration message attached: Type
1 [0203] `11` re-configuration message attached: Type 2
[0204] The re-configuration message can contain changes to the
existing assignment, or future assignments including for example:
[0205] Mobile power header room; [0206] Update of capabilities;
[0207] Request for different MIMO mode; [0208] Request for
different MCS; [0209] Indication of mobile data backlog size;
[0210] Indication to continue assigning UL resources until data
backlog is emptied; [0211] Resource size specification; [0212]
Delay requirement, QoS, etc.; [0213] Request of an additional
service/resource; [0214] Other transmission parameters.
[0215] In some embodiments, the header (and possible message) is
added to only a first packet transmission, for example the first
packet in a series of packet transmissions (talk spurt, file
download, etc.)
[0216] In some embodiments, the header (and possible message) is
added to the first packet transmission, and every N.sup.th packet
afterwards, where N can be one or larger.
[0217] ACK/NAK of packet transmission from the base station can be
used to provide the access terminal with an indication that the
re-configuration message was correctly received.
Renewal of Service 216
[0218] A renewal for service is signaling transmitted by the access
terminal to the base station to indicate a renewal of a configured
service. Because it is simply a renewal, the message size can be
very small; for example, details such as a size of a requested
allocation do not need to be included. The specifics of the channel
for transmitting this are implementation specific. Several specific
options, each of which will be described in detail below, include:
[0219] Option 1: use UL control resource [0220] Option 2: use
random access channel with scrambling sequences
Option 1--Renewal Uses UL Control Resource
[0221] In this embodiment, after an access terminal has received a
UL assignment for a given type of service, the assignment can be
renewed through a single renewal message. An existing assignment
may have expired, or been stopped (e.g., Silence period in VoIP) or
may have only existed for one packet and its HARQ transmissions. In
some embodiments the renewal message is simply an ON/OFF toggle to
renew service with previous or existing parameters. With this
embodiment, the renewal message is sent using part of a
persistently assigned UL control resource space. The message may
have a message type to indicate that service renewal is being
signaled. In some embodiments, an access terminal can be assigned
multiple messages to allow toggling of multiple services. In some
embodiments, a downlink feedback field is replaced with the renewal
message.
[0222] In some embodiments, the parameters of the renewal process
(i.e., location in the control resource allocated for renewal) for
a first transmission are set to a default. In some embodiments,
re-configuration in a first transmission can be used to provide
parameter changes.
[0223] This approach is useful, for example, for an access terminal
to switch a VoIP service from inactive to active state.
Option 2--Renewal Uses Use Random Access Channel with Scrambling
Sequences
[0224] After an access terminal has received a UL assignment for a
given type of service, the service can be renewed through a single
message. The message may be a simple an ON/OFF toggle to renewal
service with previous or existing parameters. In this embodiment,
the message is sent using a resource request using a random access
resource, such as described above for example, to renew service to
the last set of configuration parameters.
[0225] In some embodiments, an access terminal can be assigned
multiple messages to allow toggling of multiple services.
[0226] In some embodiments, the parameters of the renewal process
for a first transmission are set to default values.
System with Two Mechanisms for Resource Requests and Renewal
Requests
[0227] Details have been provided above of the use of a contention
based channel (random access channel) approach for resource
requests and the use of a contention based channel (random access
channel approach for renewal requests. In addition, details have
been provided above of the use of control resources for resource
requests, and the use of control resources for renewal requests. In
another embodiment, two different mechanisms are implemented one of
which is contention based, and the other of which uses UL control
resources, and a given access terminal chooses between the two
mechanisms.
First Mechanism: Contention Based Mechanism for Resource Requests
and Renewal Requests
[0228] An indication is sent to the base station specifying that
the access terminal requires a resource assignment. The base
station responds with an allocation of a preconfigured resource
assignment, a renewal of an existing service, or a default
allocation. The further configuration of the resource request can
be specified in a MAC message embedded in the transmissions.
[0229] The indication occurs using the access channel signaling
ID's, but is scrambled by a resource renewal or resource request
specific scrambling sequence. In some embodiments, such an
indication can also or alternatively be sent on the access terminal
specific UL resources.
Second Mechanism: UL Control Resource for Resource/Renewal Request
Message
[0230] A message is sent to the base station specifying that the
access terminal requires a resource assignment along with some
parameters of the assignment such as delay constraints, QoS, packet
backlog, resource size, etc., to name a few examples of what might
be included. This message is sent on the access terminal specific
UL control resources.
[0231] With this embodiment, the access terminal can choose the
form (indication vs. message) and location (random access channel
vs. UL control resource) of the transmission. For example, in some
cases, the access terminal's assigned UL control resources may
occur infrequently, in which case the access terminal might select
the random access channel mechanism.
[0232] In some embodiments, the sequences are scrambled by sector
ID and access/request type. For resource request channel, the
request type specifies a request for a pre-configured service or
assignment. Multiple request types can distinguish between requests
for different services, such as VoIP, data traffic, etc.
Example of a Physical Structure for Uplink Signaling
[0233] A detailed example of another physical structure for uplink
signaling will now be described. This can be used for some of the
UL signaling/resource requests described previously and/or for
other uplink signaling purposes such as ACK/NAK, CQI feedback,
resources requests, etc. to name a few specific examples.
[0234] In some embodiments, the uplink signaling method described
here can be used as a mechanism by which the access terminal
signals the base station (or other serving transmitter) and
uniquely identifies itself to the base station in the process. In
this manner the base station knows which specific access terminal
sent the UL signaling, and may take appropriate action (for
example, a predefined response).
[0235] A resource is assigned for uplink signaling, for example
resource requests that includes a single tile or multiple
distributed tiles, where a tile is physically contiguous set of
subcarriers and OFDM symbols within a resource set. A specific
example is depicted in FIG. 21 in which each tile is 6 subcarriers
by 6 symbols, and three such tiles 280, 282, 284 are available for
uplink signaling within a subframe or frame.
[0236] In some embodiments each tile is divided into different
sections. In the illustrated example, each tile 280, 282, 284 is
divided into two sections--a first section occurring over the first
three OFDM symbols generally indicated at 290 and a second section
occurring over the second three OFDM symbols generally indicated at
292. It should be apparent that this approach can be generalized to
the division of tiles into a plurality of sections.
[0237] In some embodiments, an access terminal is assigned a
respective sequence to be used for UL signaling in each section of
the tile. For example, in tile 280, the access terminal uses a
sequence from a first sequence set of L.sub.1 sequences in section
294, and uses a sequence from a second sequence set of L.sub.2
sequences in section 296. The two sequence sets may be the same or
different. The number of permutations of pairs of sequences
including a sequence from the first set and a sequence from the
second set is L.sub.1.times.L.sub.2. Each access terminal is
uniquely identified by the pair of sequences used. In some cases,
more than one access terminal may be assigned the same sequence in
one or more of the sequence sets, but not in all sequence sets.
[0238] In some embodiments, the mapping of sequences to the tile is
repeated to other distributed tiles to exploit frequency diversity.
For example, the access terminal that employs tile 280 to transmit
its sequences may also use tiles 282 and 284.
[0239] In some embodiments, there may be multiple sets of tiles for
signaling. The particular set of tiles assigned to the access
terminal, in combination with the sequences assigned, uniquely
identify the access terminal.
[0240] In some embodiments, the spreading sequences used may be
orthogonal sequences.
[0241] In some embodiments, the manner by which the sequences are
mapped can be changed from tile to tile. This is depicted in the
example illustrated in FIG. 20 in which the area for the first
sequence set occurs during the first three OFDM symbols 290 for
tiles 280, 284, and occurs during the second three OFDM symbols 292
for tile 282, and in which the area for the second sequence set
occurs during the second three OFDM symbols 292 for tiles 280, 284,
and occurs during the first three OFDM symbols 290 for tile
282.
[0242] While the example has focused on the use of this uplink
signaling method specifically for resource requests, it can be used
for other purposes such as periodic ranging, ranging, CQI feedback,
or other notification from the access terminal.
[0243] Some embodiments have included the multiplexing of initial
access channels and resource request in the same resource, and/or
using the same sequences. In some embodiments, the resource request
channel is configured according to embodiments described, but
independently of the initial access channel which may or may not be
present, or other channels described herein. For example, in some
embodiments the resource request channel can have structure
according to the embodiment described, whereas the random access
channel uses an unrelated structure. In addition, in some
embodiments it may not be appropriate to share the same OFDM symbol
structure for resource request and initial access channels. In
these case, the resource request channel, or access channels, can
be implemented according to the embodiments herein but applied to
each channel independently.
Wireless System Overview
[0244] Referring to the drawings, FIG. 1 shows a base station
controller (BSC) 10 which controls wireless communications within
multiple cells 12, which cells are served by corresponding base
stations (BS) 14. In some configurations, each cell is further
divided into multiple sectors 13 or zones (not shown). In general,
each base station 14 facilitates communications using OFDM with
mobile and/or wireless terminals 16 (more generally access
terminals), which are within the cell 12 associated with the
corresponding base station 14. The movement of the mobile stations
16 in relation to the base stations 14 results in significant
fluctuation in channel conditions. As illustrated, the base
stations 14 and mobile stations 16 may include multiple antennas to
provide spatial diversity for communications. In some
configurations, relay stations 15 may assist in communications
between base stations 14 and wireless terminals 16. Wireless
terminals 16 can be handed off 18 from any cell 12, sector 13, zone
(not shown), base station 14 or relay 15 to an other cell 12,
sector 13, zone (not shown), base station 14 or relay 15. In some
configurations, base stations 14 communicate with each and with
another network (such as a core network or the internet, both not
shown) over a backhaul network 11. In some configurations, a base
station controller 10 is not needed.
[0245] With reference to FIG. 2, an example of a base station 14 is
illustrated. The base station 14 generally includes a control
system 20, a baseband processor 22, transmit circuitry 24, receive
circuitry 26, multiple antennas 28, and a network interface 30. The
receive circuitry 26 receives radio frequency signals bearing
information from one or more remote transmitters provided by mobile
stations 16 (illustrated in FIG. 3) and relay stations 15
(illustrated in FIG. 4). A low noise amplifier and a filter (not
shown) may cooperate to amplify and remove broadband interference
from the signal for processing. Down conversion and digitization
circuitry (not shown) will then down convert the filtered, received
signal to an intermediate or baseband frequency signal, which is
then digitized into one or more digital streams.
[0246] The baseband processor 22 processes the digitized received
signal to extract the information or data bits conveyed in the
received signal. This processing typically comprises demodulation,
decoding, and error correction operations. As such, the baseband
processor 22 is generally implemented in one or more digital signal
processors (DSPs) or application-specific integrated circuits
(ASICs). The received information is then sent across a wireless
network via the network interface 30 or transmitted to another
mobile station 16 serviced by the base station 14, either directly
or with the assistance of a relay 15.
[0247] On the transmit side, the baseband processor 22 receives
digitized data, which may represent voice, data, or control
information, from the network interface 30 under the control of
control system 20, and encodes the data for transmission. The
encoded data is output to the transmit circuitry 24, where it is
modulated by one or more carrier signals having a desired transmit
frequency or frequencies. A power amplifier (not shown) will
amplify the modulated carrier signals to a level appropriate for
transmission, and deliver the modulated carrier signals to the
antennas 28 through a matching network (not shown). Modulation and
processing details are described in greater detail below.
[0248] With reference to FIG. 3, an example of a mobile station 16
is illustrated. Similar to the base station 14, the mobile station
16 will include a control system 32, a baseband processor 34,
transmit circuitry 36, receive circuitry 38, multiple antennas 40,
and mobile station interface circuitry 42. The receive circuitry 38
receives radio frequency signals bearing information from one or
more base stations 14 and relays 15. A low noise amplifier and a
filter (not shown) may cooperate to amplify and remove broadband
interference from the signal for processing. Down conversion and
digitization circuitry (not shown) will then down convert the
filtered, received signal to an intermediate or baseband frequency
signal, which is then digitized into one or more digital
streams.
[0249] The baseband processor 34 processes the digitized received
signal to extract the information or data bits conveyed in the
received signal. This processing typically comprises demodulation,
decoding, and error correction operations. The baseband processor
34 is generally implemented in one or more digital signal
processors (DSPs) and application specific integrated circuits
(ASICs).
[0250] For transmission, the baseband processor 34 receives
digitized data, which may represent voice, video, data, or control
information, from the control system 32, which it encodes for
transmission. The encoded data is output to the transmit circuitry
36, where it is used by a modulator to modulate one or more carrier
signals that is at a desired transmit frequency or frequencies. A
power amplifier (not shown) will amplify the modulated carrier
signals to a level appropriate for transmission, and deliver the
modulated carrier signal to the antennas 40 through a matching
network (not shown). Various modulation and processing techniques
available to those skilled in the art are used for signal
transmission between the mobile station and the base station,
either directly or via the relay station.
[0251] In OFDM modulation, the transmission band is divided into
multiple, orthogonal carrier waves. Each carrier wave is modulated
according to the digital data to be transmitted. Because OFDM
divides the transmission band into multiple carriers, the bandwidth
per carrier decreases and the modulation time per carrier
increases. Since the multiple carriers are transmitted in parallel,
the transmission rate for the digital data, or symbols, on any
given carrier is lower than when a single carrier is used.
[0252] OFDM modulation utilizes the performance of an Inverse Fast
Fourier Transform (IFFT) on the information to be transmitted. For
demodulation, the performance of a Fast Fourier Transform (FFT) on
the received signal recovers the transmitted information. In
practice, the IFFT and FFT are provided by digital signal
processing carrying out an Inverse Discrete Fourier Transform
(IDFT) and Discrete Fourier Transform (DFT), respectively.
Accordingly, the characterizing feature of OFDM modulation is that
orthogonal carrier waves are generated for multiple hands within a
transmission channel. The modulated signals are digital signals
having a relatively low transmission rate and capable of staying
within their respective bands. The individual carrier waves are not
modulated directly by the digital signals. Instead, all carrier
waves are modulated at once by IFFT processing.
[0253] In operation, in some embodiments, OFDM is used for at least
downlink transmission from the base stations 14 to the mobile
stations 16. Each base station 14 is equipped with "n" transmit
antennas 28 (n.gtoreq.1), and each mobile station 16 is equipped
with "m" receive antennas 40 (m.gtoreq.1). Notably, the respective
antennas can be used for reception and transmission using
appropriate duplexers or switches and are so labelled only for
clarity.
[0254] When relay stations 15 are used, OFDM is preferably used for
downlink transmission from the base stations 14 to the relays 15
and from relay stations 15 to the mobile stations 16.
[0255] With reference to FIG. 4, an example of a relay station 15
is illustrated. Similar to the base station 14, and the mobile
station 16, the relay station 15 will include a control system 132,
a baseband processor 134, transmit circuitry 136, receive circuitry
138, multiple antennas 130, and relay circuitry 142. The relay
circuitry 142 enables the relay 14 to assist in communications
between a base station 16 and mobile stations 16. The receive
circuitry 138 receives radio frequency signals bearing information
from one or more base stations 14 and mobile stations 16. A low
noise amplifier and a filter (not shown) may cooperate to amplify
and remove broadband interference from the signal for processing.
Down conversion and digitization circuitry (not shown) will then
down convert the filtered, received signal to an intermediate or
baseband frequency signal, which is then digitized into one or more
digital streams.
[0256] The baseband processor 134 processes the digitized received
signal to extract the information or data bits conveyed in the
received signal. This processing typically comprises demodulation,
decoding, and error correction operations. The baseband processor
134 is generally implemented in one or more digital signal
processors (DSPs) and application specific integrated circuits
(ASICs).
[0257] For transmission, the baseband processor 134 receives
digitized data, which may represent voice, video, data, or control
information, from the control system 132, which it encodes for
transmission. The encoded data is output to the transmit circuitry
136, where it is used by a modulator to modulate one or more
carrier signals that is at a desired transmit frequency or
frequencies. A power amplifier (not shown) will amplify the
modulated carrier signals to a level appropriate for transmission,
and deliver the modulated carrier signal to the antennas 130
through a matching network (not shown). Various modulation and
processing techniques available to those skilled in the art are
used for signal transmission between the mobile station and the
base station, either directly or indirectly via a relay station, as
described above.
[0258] With reference to FIG. 5, a logical OFDM transmission
architecture will be described. Initially, the base station
controller 10 will send data to be transmitted to various mobile
stations 16 to the base station 14, either directly or with the
assistance of a relay station 15. The base station 14 may use the
channel quality indicators (CQIs) associated with the mobile
stations to schedule the data for transmission as well as select
appropriate coding and modulation for transmitting the scheduled
data. The CQIs may be directly from the mobile stations 16 or
determined at the base station 14 based on information provided by
the mobile stations 16. In either case, the CQI for each mobile
station 16 is a function of the degree to which the channel
amplitude (or response) varies across the OFDM frequency band.
[0259] Scheduled data 44, which is a stream of bits, is scrambled
in a manner reducing the peak-to-average power ratio associated
with the data using data scrambling logic 46. A cyclic redundancy
check (CRC) for the scrambled data is determined and appended to
the scrambled data using CRC adding logic 48. Next, channel coding
is performed using channel encoder logic 50 to effectively add
redundancy to the data to facilitate recovery and error correction
at the mobile station 16. Again, the channel coding for a
particular mobile station 16 is based on the CQI. In some
implementations, the channel encoder logic 50 uses known Turbo
encoding techniques. The encoded data is then processed by rate
matching logic 52 to compensate for the data expansion associated
with encoding.
[0260] Bit interleaver logic 54 systematically reorders the bits in
the encoded data to minimize the loss of consecutive data bits. The
resultant data bits are systematically mapped into corresponding
symbols depending on the chosen baseband modulation by mapping
logic 56. Preferably, Quadrature Amplitude Modulation (QAM) or
Quadrature Phase Shift Key (QPSK) modulation is used. The degree of
modulation is preferably chosen based on the CQI for the particular
mobile station. The symbols may be systematically reordered to
further bolster the immunity of the transmitted signal to periodic
data loss caused by frequency selective fading using symbol
interleaver logic 58.
[0261] At this point, groups of bits have been mapped into symbols
representing locations in an amplitude and phase constellation.
When spatial diversity is desired, blocks of symbols are then
processed by space-time block code (STC) encoder logic 60, which
modifies the symbols in a fashion making the transmitted signals
more resistant to interference and more readily decoded at a mobile
station 16. The STC encoder logic 60 will process the incoming
symbols and provide "n" outputs corresponding to the number of
transmit antennas 28 for the base station 14. The control system 20
and/or baseband processor 22 as described above with respect to
FIG. 5 will provide a mapping control signal to control STC
encoding. At this point, assume the symbols for the "n" outputs are
representative of the data to be transmitted and capable of being
recovered by the mobile station 16.
[0262] For the present example, assume the base station 14 has two
antennas 28 (n=2) and the STC encoder logic 60 provides two output
streams of symbols. Accordingly, each of the symbol streams output
by the STC encoder logic 60 is sent to a corresponding IFFT
processor 62, illustrated separately for ease of understanding.
Those skilled in the art will recognize that one or more processors
may be used to provide such digital signal processing, alone or in
combination with other processing described herein. The IFFT
processors 62 will preferably operate on the respective symbols to
provide an inverse Fourier Transform. The output of the IFFT
processors 62 provides symbols in the time domain. The time domain
symbols are grouped into frames, which are associated with a prefix
by prefix insertion logic 64. Each of the resultant signals is
up-converted in the digital domain to an intermediate frequency and
converted to an analog signal via the corresponding digital
up-conversion (DUC) and digital-to-analog (D/A) conversion
circuitry 66. The resultant (analog) signals are then
simultaneously modulated at the desired RF frequency, amplified,
and transmitted via the RF circuitry 68 and antennas 28. Notably,
pilot signals known by the intended mobile station 16 are scattered
among the sub-carriers. The mobile station 16, which is discussed
in detail below, will use the pilot signals for channel
estimation.
[0263] Reference is now made to FIG. 6 to illustrate reception of
the transmitted signals by a mobile station 16, either directly
from base station 14 or with the assistance of relay 15. Upon
arrival of the transmitted signals at each of the antennas 40 of
the mobile station 16, the respective signals are demodulated and
amplified by corresponding RF circuitry 70. For the sake of
conciseness and clarity, only one of the two receive paths is
described and illustrated in detail. Analog-to-digital (A/D)
converter and down-conversion circuitry 72 digitizes and down
converts the analog signal for digital processing. The resultant
digitized signal may be used by automatic gain control circuitry
(AGC) 74 to control the gain of the amplifiers in the RF circuitry
70 based on the received signal level.
[0264] Initially, the digitized signal is provided to
synchronization logic 76, which includes coarse synchronization
logic 78, which buffers several OFDM symbols and calculates an
auto-correlation between the two successive OFDM symbols. A
resultant time index corresponding to the maximum of the
correlation result determines a fine synchronization search window,
which is used by fine synchronization logic 80 to determine a
precise framing starting position based on the headers. The output
of the fine synchronization logic 80 facilitates frame acquisition
by frame alignment logic 84. Proper framing alignment is important
so that subsequent FFT processing provides an accurate conversion
from the time domain to the frequency domain. The fine
synchronization algorithm is based on the correlation between the
received pilot signals carried by the headers and a local copy of
the known pilot data. Once frame alignment acquisition occurs, the
prefix of the OFDM symbol is removed with prefix removal logic 86
and resultant samples are sent to frequency offset correction logic
88, which compensates for the system frequency offset caused by the
unmatched local oscillators in the transmitter and the receiver.
Preferably, the synchronization logic 76 includes frequency offset
and clock estimation logic 82, which is based on the headers to
help estimate such effects on the transmitted signal and provide
those estimations to the correction logic 88 to properly process
OFDM symbols.
[0265] At this point, the OFDM symbols in the time domain are ready
for conversion to the frequency domain using FFT processing logic
90. The results are frequency domain symbols, which are sent to
processing logic 92. The processing logic 92 extracts the scattered
pilot signal using scattered pilot extraction logic 94, determines
a channel estimate based on the extracted pilot signal using
channel estimation logic 96, and provides channel responses for all
sub-carriers using channel reconstruction logic 98. In order to
determine a channel response for each of the sub-carriers, the
pilot signal is essentially multiple pilot symbols that are
scattered among the data symbols throughout the OFDM sub-carriers
in a known pattern in both time and frequency. Continuing with FIG.
6, the processing logic compares the received pilot symbols with
the pilot symbols that are expected in certain sub-carriers at
certain times to determine a channel response for the sub-carriers
in which pilot symbols were transmitted. The results are
interpolated to estimate a channel response for most, if not all,
of the remaining sub-carriers for which pilot symbols were not
provided. The actual and interpolated channel responses are used to
estimate an overall channel response, which includes the channel
responses for most, if not all, of the sub-carriers in the OFDM
channel.
[0266] The frequency domain symbols and channel reconstruction
information, which are derived from the channel responses for each
receive path are provided to an STC decoder 100, which provides STC
decoding on both received paths to recover the transmitted symbols.
The channel reconstruction information provides equalization
information to the STC decoder 100 sufficient to remove the effects
of the transmission channel when processing the respective
frequency domain symbols.
[0267] The recovered symbols are placed back in order using symbol
de-interleaver logic 102, which corresponds to the symbol
interleaver logic 58 of the transmitter. The de interleaved symbols
are then demodulated or de-mapped to a corresponding bit stream
using de-mapping logic 104. The bits are then de-interleaved using
bit de-interleaver logic 106, which corresponds to the bit
interleaver logic 54 of the transmitter architecture. The
de-interleaved bits are then processed by rate de-matching logic
108 and presented to channel decoder logic 110 to recover the
initially scrambled data and the CRC checksum. Accordingly, CRC
logic 112 removes the CRC checksum, checks the scrambled data in
traditional fashion, and provides it to the de-scrambling logic 114
for de-scrambling using the known base station de-scrambling code
to recover the originally transmitted data 116.
[0268] In parallel to recovering the data 116, a CQI, or at least
information sufficient to create a CQI at the base station 14, is
determined and transmitted to the base station 14. As noted above,
the CQI may be a function of the carrier-to-interference ratio
(CR), as well as the degree to which the channel response varies
across the various sub-carriers in the OFDM frequency band. For
this embodiment, the channel gain for each sub-carrier in the OFDM
frequency band being used to transmit information is compared
relative to one another to determine the degree to which the
channel gain varies across the OFDM frequency band. Although
numerous techniques are available to measure the degree of
variation, one technique is to calculate the standard deviation of
the channel gain for each sub-carrier throughout the OFDM frequency
band being used to transmit data.
[0269] In some embodiments, a relay station may operate in a time
division manner using only one radio, or alternatively include
multiple radios.
[0270] FIGS. 1 to 6 provide one specific example of a communication
system that could be used to implement embodiments of the
application. It is to be understood that embodiments of the
application can be implemented with communications systems having
architectures that are different than the specific example, but
that operate in a manner consistent with the implementation of the
embodiments as described herein.
[0271] Numerous modifications and variations of the present
invention are possible in light of the above teachings. It is
therefore to be understood that within the scope of the appended
claims, the invention may be practiced otherwise than as
specifically described herein.
* * * * *