U.S. patent application number 10/675565 was filed with the patent office on 2004-07-08 for adaptive link layer for point to multipoint communication system.
This patent application is currently assigned to Aperto Networks, Inc.. Invention is credited to Fuentes, Jean, Ngo, Khuong, Reza, Majidi-Ahy, Truong, Paul, Varma, Subir.
Application Number | 20040132459 10/675565 |
Document ID | / |
Family ID | 23888487 |
Filed Date | 2004-07-08 |
United States Patent
Application |
20040132459 |
Kind Code |
A1 |
Varma, Subir ; et
al. |
July 8, 2004 |
Adaptive link layer for point to multipoint communication
system
Abstract
The invention provides a method and system for a wireless
transport layer, such as for use in a wireless communication
system. In a preferred embodiment, the wireless transport layer
includes the capability for instructing customer premises equipment
to adjust the physical characteristics on its communication link
with the base station controller, and for instructing customer
premises equipment to conduct further communications using those
new physical characteristics. The wireless transport layer includes
a number of provisions for adjusting communication between the base
station controller and customer premises equipment in view of the
prospect of adjusting physical characteristics for communication
between the two end points. The use of a point-to-multipoint
wireless channel provides services over a link whose parameters are
continuously adapting to current conditions on a per-user
basis.
Inventors: |
Varma, Subir; (San Jose,
CA) ; Ngo, Khuong; (San Jose, CA) ; Fuentes,
Jean; (Santa Clara, CA) ; Truong, Paul; (San
Jose, CA) ; Reza, Majidi-Ahy; (Los Altos,
CA) |
Correspondence
Address: |
SWERNOFSKY LAW GROUP PC
P.O. BOX 390013
MOUNTAIN VIEW
CA
94039-0013
US
|
Assignee: |
Aperto Networks, Inc.
1637 South Main Street
Milpitas
CA
|
Family ID: |
23888487 |
Appl. No.: |
10/675565 |
Filed: |
September 30, 2003 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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10675565 |
Sep 30, 2003 |
|
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09475642 |
Dec 30, 1999 |
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6650623 |
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Current U.S.
Class: |
455/452.2 |
Current CPC
Class: |
H04L 1/0025 20130101;
H04L 2001/0093 20130101; H04L 1/0002 20130101; H04W 48/08 20130101;
H04W 52/50 20130101; H04W 28/18 20130101; H04L 1/16 20130101; H04W
4/06 20130101 |
Class at
Publication: |
455/452.2 |
International
Class: |
H04Q 007/20 |
Claims
1. A method, including steps of determining first values for a set
of parameters for a communication link, in a first layer of an OSI
model communication system; sending information using said first
values; obtaining information regarding characteristics of said
communication link; and adjusting said first values in response to
said information, whereby further use of said communication link is
responsive to said steps of adjusting.
2. A method is in claim 1, wherein said first values include at
least two of: an antenna selection value, a power level value, a
channel selection value, a modulation type value, a symbol rate
value, an error code type value, a set of equalization values.
3. A method as in claim 1, including steps of determining
alternative values for said set of parameters for a second
communication link in said communication system; sending
information using said second communication link; obtaining
alternative information regarding characteristics of said second
communication link; and adjusting said alternative values in
response to said alternative information, whereby further use of
said second communication link is responsive to said steps of
adjusting.
4. A method as in claim 3, wherein said steps of adjusting said
alternative values are responsive to a result of said steps of
adjusting said first values.
5. A method as in claim 3, wherein said steps of determining
alternative values are responsive to a result of said steps of
determining first values.
6. A method as in claim 1, including steps of determining second
values for a set of parameters for communication link, in a second
layer of said communication system; adjusting said second values
and responses said information; and wherein said steps of sending
information use said second values.
7. A method is in claim 6, wherein said first layer includes a
media access layer; and said second layer includes at least one of:
a physical layer, a network layer, a transport layer, an
application layer.
8. A method is in claim 6, wherein said first layer includes a
physical layer; and said second layer includes at least one of: a
media access layer, a network layer, a transport layer, an
application layer.
9. A method is in claim 1, wherein said second values include at
least one of: a message size value, a set of acknowledgment and
retransmission values, a TDD duty cycle value.
10. A method as in claim 1, wherein said steps of adjusting include
determining second values in response to said information; and
combining said first values and said second values; whereby said
first values are adjusted in response to a result of said steps of
combining.
11. A method is in claim 10, wherein said steps of combining
include adaptively altering said first values using at least one
hysteresis parameter.
12. A method is in claim 1, wherein said steps of determining are
responsive to a higher-level layer in said communication
system.
13. A method is in claim 12, wherein said first layer includes a
media access layer; and said second layer includes at least one of:
a network layer, a transport layer, an application layer.
14. A method is in claim 12, wherein said first layer includes a
physical layer; and said higher-level layer includes at least one
of: a media access layer, a network layer, a transport layer, an
application layer.
15. A method, including steps of dynamically determining
characteristics of a communication link between a first device to a
second device; dynamically sending first information regarding said
characteristics from said first device to said second device;
receiving said information at said second device; dynamically
sending second information between said first device and said
second device using said characteristics, in response to said first
information.
16. A method as in claim 15, wherein said communication link
includes a wireless communication link.
17. A method as in claim 15, wherein said communication link
includes a time division multiple access communication link.
18. A method as in claim 15, wherein said first information
includes a plurality of said characteristics, each one of said
plurality of characteristics possibly being different from each
other one of said plurality of characteristics; each one of said
plurality of characteristics being specific to one said second
device of a plurality of said second devices.
19. A method as in claim 15, including the steps of choosing a
timebase to allow for link adaptation in such a way that said
chosen time base is independent of the said communication link
parameters; fragmentation and reassembly of data units in such a
way that the fragment size (measured in ticks) remains constant
regardless of the nature of said communication link parameters.
20. A method as in claim 15, wherein said communication link
parameters are responsive to the relative frequency with which
packets are dropped, rather than responsive to various other
measurements.
21. A method as in claim 15, wherein said communication link
includes a portion of a duplex communication link, said duplex
communication link having a structure including sequential frames;
said first information is sent from said first device to one or
more said second devices during a designated frame of said duplex
communication link; said first information is used to control said
steps of dynamically sending second information during said same
designated frame of said duplex communication link.
22. A method as in claim 21, wherein said sequential frames include
frame descriptor packets that describe the contents of the next
said sequential frame.
23. A method as in claim 21, wherein said duplex communication link
includes, for each said frame, a downstream portion and an upstream
portion; said first information is sent during said downstream
portion of said designated frame; said steps of dynamically sending
include sending information during said downstream portion of said
same designated frame or said upstream portion of said same
designated frame.
24. A method as in claim 15, wherein said communication link
includes a sequence of frames, each having a map section and one or
more payload elements; said first information is sent during said
map section of a designated frame; and said steps of dynamically
sending include sending information during said payload elements of
said same designated frame.
25. A method as in claim 15, wherein said steps of dynamically
sending include requesting upstream bandwidth in such a way that
the number of said payload elements is expressed as a number of
bytes rather than a number of packets.
26. A method as in claim 15, wherein the step of dynamically
sending includes sending a Sync packet that synchronizes said first
device and said second device.
27. Apparatus including means for dynamically determining
characteristics of a communication link between a first device to a
second device; means for dynamically sending first information
regarding said characteristics from said first device to said
second device; means for receiving said information at said second
device; means for dynamically sending second information between
said first device and said second device using said
characteristics, in response to said first information.
28. Apparatus including a first device capable of sending
information to a second device using a communication link; said
first device being capable of dynamically determining
characteristics of said communication link for use in communicating
with said second device; said first device being capable of
formatting first information for sending to said second device
regarding said characteristics, and capable of at least one of (a)
formatting second information for sending to said second device
using said characteristics, or (b) receiving information from said
second device using said characteristics.
29. Apparatus as in claim 28, wherein said first device includes a
transmitter for sending information using a wireless communication
link.
30. Apparatus as in claim 28, wherein said first device includes a
timer for sending or receiving information using a time division
multiple access communication link.
31. In a method for sending information between a first device to a
second device, a data structure including a frame in a sequence of
frames for transmission, each said individual frame including first
information regarding characteristics of a communication link
between said first device and said second device; second
information for communication between said first device and said
second device, said second information using said characteristics
from said same individual frame.
32. A data structure as in claim 31, wherein said communication
link includes a wireless communication link.
33. A data structure as in claim 31, wherein said communication
link includes a allocated duration of time within said same
individual frame.
34. A data structure as in claim 31, wherein said frame includes a
time division multiple access communication link.
35. A data structure as in claim 31, wherein said first information
includes a plurality of said characteristics for a corresponding
plurality of said communication links between said first device and
a corresponding plurality of said second devices.
Description
[0001] This application hereby incorporates by reference and claims
benefit of U.S. application Ser. No. 09/475,642, filed Dec. 30,
1999 (Attorney Docket No. 164.1002.01).
BACKGROUND OF THE INVENTION
[0002] The application is submitted in the name of the following
inventor(s):
1 Inventor Citizenship Residence City and State Subir VARMA United
States San Jose, CA Jean FUENTES United States Santa Clara, CA
Khuong NGO United States San Jose, CA Paul TRUONG United States San
Jose, CA Reza MAJIDI-AHY United States Los Altos, CA
[0003] 1. Field of the Invention
[0004] This invention relates to a link layer, such as for use in a
wireless communication system.
[0005] 2. Related Art
[0006] Wireless communication between a sender and a receiver
includes sending information using a wireless communication link,
in which the sender modulates information onto a wireless
communication channel (such as a frequency band reserved for
wireless communication between the sender and the receiver). The
receiver demodulates that information from the wireless
communication channel, so as to recover the original
information.
[0007] One problem with known systems is that physical
characteristics of the communication link between the sender and
receiver can change substantially over relatively short periods of
time. For example, the distance between the sender and receiver can
change. In a second example, the equipment used by the sender or
receiver (that is the consumer premises equipment) can change.
Moreover, these physical characteristics can change independently
of each other. As a result, selection of a single set of such
physical characteristics can result in relatively ineffective or
inefficient communication between the sender and the receiver.
[0008] Accordingly, it would be advantageous to provide a technique
for wireless communication, in which physical characteristics of
the communication link between sender and receiver can be changed
substantially during a single session of communication, that is not
subject to the drawbacks of the known art.
SUMMARY OF THE INVENTION
[0009] The invention provides a method and system for a wireless
transport layer, such as for use in a wireless communication
system. In a preferred embodiment, the wireless transport layer
includes the capability for instructing customer premises equipment
to adjust the physical characteristics on its communication link
with the base station controller, and for instructing customer
premises equipment to conduct further communications using those
new physical characteristics. In several aspects of the invention,
as described herein, the wireless transport layer includes a number
of provisions, such as adaptive link layer transport services and
an advanced TDMA (time division multiple access) protocol. These
work together to adjust communication between the base station
controller and customer premises equipment in view of the prospect
of adjusting physical characteristics for communication between the
two end points. The use of a point-to-multipoint wireless channel
provides services over a link whose parameters are continuously
adapting to current conditions, on a per-user basis.
[0010] The invention provides an enabling technology for a wide
variety of applications for communication, so as to obtain
substantial advantages and capabilities that are novel and
non-obvious in view of the known art. Examples described below
primarily relate to a wireless communication system, but the
invention is broadly applicable to many different types of
communication in which characteristics of the communication link
are subject to change.
BRIEF DESCRIPTION OF THE DRAWINGS
[0011] FIG. 1 shows a block diagram of a system using a new
wireless transport layer in a wireless communication system.
[0012] FIG. 2 shows a timing diagram of a TDMA frame using a new
wireless transport layer in a wireless communication system.
[0013] FIG. 3 shows a process flow diagram of a method for
operating a system using a new wireless transport layer in a
wireless communication system.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT
[0014] In the following description, a preferred embodiment of the
invention is described with regard to preferred process steps and
data structures. Embodiments of the invention can be implemented
using general-purpose processors or special purpose processors
operating under program control, or other circuits, adapted to
particular process steps and data structures described herein.
Implementation of the process steps and data structures described
herein would not require undue experimentation or further
invention.
[0015] Related Application
[0016] Inventions described herein can be used in conjunction with
inventions described in the following documents.
[0017] U.S. patent application Ser. No. ______, Express Mail
Mailing No. ______, filed the same day in the name of the same
inventors, attorney docket number 164.1003.01, titled "Adaptive
Point to Multipoint Communication System."
[0018] Each of these documents is hereby incorporated by reference
as if fully set forth herein.
[0019] Lexicography
[0020] The following terms refer or relate to aspects of the
invention as described below. The descriptions of general meanings
of these terms are not intended to be limiting, only
illustrative.
[0021] base station controller--in general, a device for performing
coordination and control for a wireless communication cell. There
is no particular requirement that the base station controller must
be a single device; in alternative embodiments, the base station
controller can include a portion of a single device, a combination
of multiple devices, or some hybrid thereof.
[0022] communication link--in general, an element for sending
information from a sender to a recipient. Although in a preferred
embodiment the communication links referred to are generally
wireless line of sight point-to-point communication links, there is
no particular requirement that they are so restricted.
[0023] customer premises equipment--in general, a device for
performing communication processes and tasks at a customer
location, and operating in conjunction with the base station
controller within a wireless communication cell. There is no
particular requirement that the customer premises equipment must be
a single device; in alternative embodiments, the customer premises
equipment can include a portion of a single device, a combination
of multiple devices, or some hybrid thereof.
[0024] physical parameters--in general, with reference to a
wireless communication link, a set of characteristics or parameters
relating to physical transmission of information on a communication
link. For example, physical characteristics can include (a) a
symbol transmission rate, (b) a number of payload data bits
assigned per symbol, (c) a number of error detection or correction
bits assigned per symbol, and the like.
[0025] wireless communication system--in general, a communication
system including at least one communication link that uses wireless
communication techniques.
[0026] wireless transport layer--in general, a set of protocols and
protocol parameters for sending and receiving information using
wireless transport. In a preferred embodiment, the wireless
transport layer is part of a multilayer systems architecture, in
which the wireless transport layer is built using a physical
transport layer, and the wireless transport layer is used by a
logical transport layer such as IP.
[0027] As noted above, these descriptions of general meanings of
these terms are not intended to be limiting, only illustrative.
Other and further applications of the invention, including
extensions of these terms and concepts, would be clear to those of
ordinary skill in the art after perusing this application. These
other and further applications are part of the scope and spirit of
the invention, and would be clear to those of ordinary skill in the
art, without further invention or undue experimentation.
[0028] System Context
[0029] A system using a wireless transport layer in a wireless
communication system operates as part of a system in which devices
coupled to a network (such as a computer network) send messages,
route and switch messages, and receive messages. Most current link
layer protocols use a simple "first come, first served" policy for
serving these messages. Other systems allow the physical link to be
divided into a number of virtual links, each with its own set of
bandwidth and QoS parameters. Unlike the existing technology, the
device described herein also includes a virtual link that describes
a set of physical layer parameters. Thus, in a preferred
embodiment, devices coupled to (and integrated with) the network
send, route, and receive these messages as sequences of packets,
each of which has a header including delivery information and a
payload including data. The packet format conforms to the OSI
model, in which an application protocol (layer 4, such as TCP) uses
a logical transport protocol (layer 3, such as IP), which uses a
physical transport protocol (layer 2), which uses a physical
transport technique (layer 1).
[0030] The system using a wireless transport layer is described
herein with regard to layer 2, particularly as it applies to
interactions with layer 1 and layer 3. However, concepts and
techniques of the invention are also applicable to other layers of
the OSI model. Adapting those concepts and techniques to such other
layers would not require undue experimentation or further
invention, and is within the scope and spirit of the invention.
[0031] System Elements
[0032] FIG. 1 shows a block diagram of a system using a new
wireless transport layer in a wireless communication system.
[0033] A system 100 includes a wireless communication cell 110, a
base station controller 120, and one or more sets of customer
premises equipment 130.
[0034] The wireless communication cell 110 includes a generally
hexagon-shaped region of local surface area, such as might be found
in a metropolitan region. Use of generally hexagon-shaped regions
is known in the art of wireless communication because they are able
to tile a local region with substantially no gaps. However,
although in a preferred embodiment the wireless communication cell
110 includes a generally hexagon-shaped region, there is no
particular requirement for using that particular shape; in
alternative embodiments it may be useful to provide another shape
or tiling of the local surface area.
[0035] The base station controller 120 includes a processor,
program and data memory, mass storage, and one or more antennas for
sending or receiving information using wireless communication
techniques.
[0036] Similar to the base station controller 120, each set of
customer premises equipment 130 includes a processor, program and
data memory, mass storage, and one or more antennas for sending or
receiving information using wireless communication techniques.
[0037] Communication among devices within the wireless
communication cell 110 is conducted on one-to-one basis between
each set of customer premises equipment 130 and the base station
controller 120. Thus, the base station controller 120 communicates
with each set of customer premises equipment 130, and each set of
customer premises equipment 130 communicates with the base station
controller 120. Customer premises equipment 130 do not communicate
directly with other customer premises equipment 130.
[0038] Communication between the base station controller 120 and
each set of customer premises equipment 130 is conducted using a
time division duplex technique, in which time duration is are
divided into individual frames, each one of which includes a
"downstream" portion and an "upstream" portion. Unlike existing
protocols in which transmissions are controlled by the transmitting
side, the base station controller 120 controls tranmissions for
both upstream and downstream directions, without specific requests
from the customer premises equipment 130.
[0039] During the downstream portion of each frame, the base
station controller 120 transmits, thus sending information to one
or more sets of customer premises equipment 130. During the
upstream portion of each frame, the base station controller
automatically allocates slots for upstream re-transmission. This
occurs in the absence of an explicit request for a slot from the
customer premises equipment 130. Particular aspects of each frame
are described with regard to FIG. 2. Time division duplex
techniques are known in the art of wireless communication.
[0040] TDMA Frame
[0041] FIG. 2 shows a timing diagram of a TDMA frame using a new
wireless transport layer in a wireless communication system.
[0042] A timing diagram 200 shows a time division multiple access
(TDMA) frame 210, including the downstream portion 220 and the
upstream portion 230. A guard band 240 separates the downstream
portion 220 from the upstream portion 230. In a preferred
embodiment, the guard band 240 has a duration at least equal to
twice the flight time of a transmission from the base station
controller 120 to the most distant customer premises equipment 130
and back.
[0043] Each frame included in a TDMA frame 210 includes a frame
descriptor packet 250 that describes the contents of the following
frame to each consumer premises equipment 130. The frame descriptor
packet 250 has several constant properties: (1) it is always the
first packet in a TDMA frame 210; and (2) it is always a fixed
size. In addition to these constants, the size of a TDMA frame 210
is also fixed and every TDMA frame always starts at times that are
multiples of the frame size. These constant properties ensure that
contact between the consumer premises equipment 130 and the base
station controller 120 is always maintained, even if one or more
frame descriptor packets 230 should get "lost".
[0044] Each frame included in the downstream portion 220 includes a
map section 221, a synchronization section 222, and one or more
downstream payload elements 223, all of which are formatted as data
packets, complete with packet headers and associated information.
An inter-payload guard band 224 separates successive downstream
payload elements 223. In a preferred embodiment, the inter-payload
guard band 224 has a duration of sixteen symbols (where the
duration of each symbol is responsive to the initial map section
221), but in alternative embodiments, the duration may take on
other values.
[0045] Each frame in the upstream portion 230 includes one or more
request sections 231, one or more acknowledgment sections 232, a
maintenance section 233, and one or more upstream payload elements
223 all of which are formatted as data packets, complete with
packet headers and associated information. Similar to the
downstream portion 220, an inter-payload guard band 224 separates
successive upstream payload elements 223.
[0046] Unlike existing systems that monitor the number of packets
that are transmitted, the system 100 monitors the number of bytes
that are transmitted. Thus, the packet sizes included in the
upstream and downstream frames can vary without breaking
protocol.
[0047] The base station controller 120 directs each set of customer
premises equipment 130 to conduct wireless communication using a
set of physical parameters and a set of MAC parameters, as selected
by the base station controller 120. Because each set of customer
premises equipment 130 is uniquely situated, the base station
controller 120 cannot generally determine a single set of physical
parameters and MAC parameters to be used by all of the customer
premises equipment 130 at once. Accordingly, the base station
controller 120 determines the individual physical parameters and
individual MAC parameters to be used by each individual set of
customer premises equipment 130. After making each such individual
determination, the base station controller 120 constructs a
descriptor, for each set of customer premises equipment 130, of
physical parameters and MAC parameters to be used by that set of
customer premises equipment 130. In a preferred embodiment, this
descriptor packet pre-announces the new set of parameters to each
transmitter or receiver device, thereby allowing them to configure
themselves to the new set of parameters. This is very different
from existing schemes which embed the parameters in the header of a
packet. Embedding the parameters in the header of a packet causes
problems because the header always has to be sent using a common
set of parameters. Moreover, using a packet header in this way does
not allow sufficient time for the transmitter or receiver to
re-configure itself for the data payload burst.
[0048] In a preferred embodiment, the physical parameters and MAC
parameters that can be tailored by a base station controller 120
include some or all or a combination of the following:
[0049] Symbol rate
[0050] Modulation
[0051] Power
[0052] Polarization
[0053] Antennae
[0054] Forward Error Correction
[0055] Packet Size
[0056] The map section 221 includes, for each set of customer
premises equipment 130, the descriptor of physical parameters and
MAC parameters to be used by that set of customer premises
equipment 130.
[0057] The synchronization section 222 is used to synchronize the
base station controller 120 clock (not shown) with clocks included
in each customer premises equipment 130 (not shown). Each
synchronization section 222 includes a set of information (such as
an equalizer training sequence) known ahead of time by each set of
customer premises equipment 130. Each set of customer premises
equipment 130 is capable of receiving the synchronization section
222 (and therefore the known information in the synchronization
section 222), and capable of synchronizing its internal clock (not
shown) to correspond with a master clock (not shown) at the base
station controller 120. For example, each set of customer premises
equipment 130 can include a phase locked loop disposed so as to
receive the synchronization section 222 and phase lock the internal
clock for that set of customer premises equipment number 130 with
the master clock at the base station controller 120. Thus, each set
of customer premises equipment 130 is frequently synchronized with
the base station controller 120. Techniques for synchronization of
distributed equipment using wireless communication are known in the
art of wireless communication.
[0058] Each downstream payload element 223 includes payload
information sent from the base station controller 120 to a specific
target set of customer premises equipment 130. The payload
information is separately formatted by the base station controller
120 in response to the physical parameters and MAC parameters for
the target customer premises equipment 130. Thus, each downstream
payload element 223 includes a sequence of symbols, each encoding a
sequence of bits, separately formatted by the base station
controller 120, transmitted by the base station controller 120, and
thus sent from the base station controller 120 to the target
customer premises equipment 130.
[0059] Those skilled in the art will recognize, after perusal of
this application, that each downstream payload element 223 is
separately formatted according to an individual set of physical
parameters and MAC parameters. Thus, each downstream payload
element 223 might have an individual duration, and even when two
downstream payload elements 223 have identical duration, might have
an individual number of symbols, an individual number of bits per
symbol, and an individual number of total bits for the downstream
payload element 223.
[0060] Those skilled in the art will recognize, after perusal of
this application, that each downstream payload element 223 is
separately received and decoded by its target customer premises
equipment 130, according to the individual set of physical
parameters and MAC parameters determined by the base station
controller 120 and sent by the base station controller 120 during
the map section 221 in the same downstream portion 220 in the same
TDMA frame 210. Thus, the base station controller 120 is able to
send information to each set of customer premises equipment 130 and
to direct each set of customer premises equipment 130 to receive
that information using an optimal set of physical parameters and
MAC parameters for that TDMA frame 210.
[0061] Similarly, the base station controller 120 directs each set
of customer premises equipment 130 to conduct communications using
the physical parameters and MAC parameters transmitted in the map
section 221 of the same TDMA frame 210. Thus, upstream payload
elements 223 sent by each individual set of customer premises
equipment 130 are formatted by each individual set of customer
premises equipment 130 using the optimal set of physical parameters
and MAC parameters (as determined by the base station controller
120) for that TDMA frame 210.
[0062] The request section 231 includes a sequence of requests to
transmit up-stream payload elements 223, as requested by each set
of customer premises equipment 130. The request section 231 is not
expressed as a unit of time or a number of packets. The request
section 231 specifically requests a number of payload bytes. This
is preferable since given that the packets are of variable size,
specifying their number does not tell the base station controller
120 about the number of bytes that need to be transmitted.
Furthermore, it is not feasible for the consumer premises equipment
130 to make requests in units of transmit time because the link
parameters assigned to the consumer premises equipment 130 change
over time. The consumer premises equipment 130 sequentially numbers
each byte and writes the sequence number of the last byte in its
buffer into the request section 231. In combination with the
sequence number of the byte being transmitted, this scheme allows
the base station controller 120 to unambiguously estimate the
current backlog in the consumer premises equipment 130.
[0063] The acknowledgment sections 232 each include an
acknowledgment message by customer premises equipment 130 not
otherwise sending an acknowledgment to the base station controller
120.
[0064] The maintenance section 233 includes maintenance information
transmitted by either the base station controller 120 or by one or
more sets of customer premises equipment 130.
[0065] Similar to the downstream payload elements 223, the upstream
payload elements 223 each includes payload information sent from
customer premises equipment 130 to the base station controller 120.
The payload information is separately formatted by each customer
premises equipment 130 in response to the physical parameters and
MAC parameters determined by the base station controller 120 for
the sending customer premises equipment 130 (and transmitted during
the map section 221). Thus, similar to each downstream payload
element 223, each upstream payload element 223 includes a sequence
of symbols, each encoding a sequence of bits, separately formatted
by the customer premises equipment 130, transmitted by the customer
premises equipment 130, and thus sent from the customer premises
equipment 130 to the base station controller 120.
[0066] Method of Operation
[0067] FIG. 3 shows a process flow diagram of a method for
operating a system using a new wireless transport layer in a
wireless communication system.
[0068] A method 300 includes a set of flow points and a set of
steps. The system 100 performs the method 300. Although the method
300 is described serially, the steps of the method 300 can be
performed by separate elements in conjunction or in parallel,
whether asynchronously, in a pipelined manner, or otherwise. There
is no particular requirement that the method 300 be performed in
the same order in which this description lists the steps, except
where so indicated.
[0069] Sending Downstream Information
[0070] At a flow point 310, the base station controller 120 is
ready to send information to one or more sets of customer premises
equipment 130.
[0071] At a step 311, the base station controller 120 determines
sets of physical parameters and MAC parameters it considers optimal
for each set of customer premises equipment 130.
[0072] At a step 312, the base station controller 120 determines
information it will send to each set of customer premises equipment
130.
[0073] At a step 313, the base station controller 120 formats the
downstream portion 220 of the TDMA frame 210. As part of this step,
the base station controller 120 formats the map section 221, to
include the physical parameters and MAC parameters it determined in
the step 311 for each individual set of customer premises equipment
130. As part of this step, the base station controller 120 formats
the synchronization section 222. As part of this step, the base
station controller 120 formats one or more downstream payload
elements 223, to include the information it determined in the step
312 for each individual set of customer premises equipment 130.
[0074] At a step 314, the base station controller 120 waits for the
guard band 340 to pass before attempting to receive information
from customer premises equipment 130. The method 300 continues with
the flow point 330 and the flow point 340.
[0075] After this step, the base station controller 120 has
performed one instance of sending information during the downstream
portion 220. The flow point 310 is reached repeatedly and the steps
thereafter are performed repeatedly, for each TDMA frame 210.
[0076] Receiving Downstream Information
[0077] At a flow point 320, preferably reached in parallel with the
flow point 310, one or more sets of customer premises equipment 130
are ready to receive information from the base station controller
120.
[0078] At a step 321, each individual customer premises equipment
130, having been earlier synchronized with the base station
controller 120, receives the map section 221, including the
physical parameters and MAC parameters the base station controller
120 considers optimal for communication with that individual of
customer premises equipment 130.
[0079] At a step 322, each individual customer premises equipment
130 receives the synchronization section 222, and re-synchronizes
its internal clock to correspond with the master clock at the base
station controller 120. Since each individual customer premises
equipment 130 can be a different distance from the base station
controller 120, each individual customer premises equipment 130
will receive the synchronization section 222 at a (slightly)
different time, and thus each individual customer premises
equipment 130 will run its internal clock at a (slightly) different
phase from the master clock at the base station controller 120.
[0080] At a step 323, each individual customer premises equipment
130 receives one or more downstream payload elements 223, using the
physical parameters and MAC parameters it received during the map
section 221.
[0081] At a step 324, each individual customer premises equipment
130 waits for the guard band 340 to pass before attempting to send
information to the base station controller 120. The method 300
continues with the flow point 330 and the flow point 340.
[0082] After this step, each individual customer premises equipment
130 has performed one instance of receiving information during the
downstream portion 220. The flow point 320 is reached repeatedly
and the steps thereafter are performed repeatedly, for each TDMA
frame 210.
[0083] Sending Upstream Information
[0084] At a flow point 330, individual customer premises equipment
130 are ready to send information to the base station controller
120.
[0085] At a step 331, each individual customer premises equipment
130 determines whether it desires to request allocation of
bandwidth for transmission during the TDMA frame 210. As part of
this step, the individual customer premises equipment 130 formats a
request for transmission during a specific request section 231
designated for use by that individual customer premises equipment
130.
[0086] At a step 332, each individual customer premises equipment
130 that desires to request allocation of bandwidth for
transmission transmits during its assigned request section 231, so
as to inform the base station controller 120 of its desire. For
example, individual customer premises equipment 130 might be given
a numeric ordering by the base station controller 120, so that each
individual customer premises equipment 130 has an assigned time
slot during which it can request bandwidth allocation from the base
station controller 120. Alternatively, individual customer premises
equipment 130 might contend for individual request sections 231,
using a "slotted aloha" technique or other known technique for
contention for limited resources.
[0087] In a alternative embodiment, the base station controller 120
determines, for each request section 231, whether that request
section 231 will be assigned to a particular customer premises
equipment 130, or will be open for contention like multiple
customer premises equipment 130. In the latter case, the base
station controller 120 determines, for those request sections 231
which are open for contention, whether contention will be limited
to particular subsets of customer premises equipment 130, or
whether contention will be open to all customer premises equipment
130.
[0088] When the base station controller 120 receives requests for
allocation of bandwidth, the base station controller 120
determines, for the following TDMA frame 210, the allocations of
bandwidth it considers optimal for particular customer premises
equipment 130. The particular allegations determined by the base
station controller 120 are transmitted during the next TDMA frame
210, during the downstream portion 220, during the map section
221.
[0089] At a step 333, each individual customer premises equipment
130 that desires to make an acknowledgment of information is
received from the base station controller 120, transmits during its
designed acknowledgment section 232, so as to inform the base
station controller 120 of its acknowledgment. In a preferred
embodiment, acknowledgement sections 232 are specifically assigned
to individual customer premises equipment 130.
[0090] In an alternative embodiment, the base station controller
120 determines, for each acknowledgment section 232, which
particular customer premises equipment 130 will have use of that
acknowledgment section 232. Moreover, in a preferred embodiment,
individual customer premises equipment 130 having allocations of
bandwidth for transmission using upstream payload elements 223 will
generally not require further bandwidth for transmission during
acknowledgments sections 232. Accordingly, the base station
controller 120 can reserve individual acknowledgment sections 232
for particular customer premises equipment 130 not already having
allocations for bandwidth for transmission using upstream payload
elements 223.
[0091] At a step 334, each individual customer premises equipment
130 determines whether it needs to transmit during the maintenance
section 233. As part of this step, each individual customer
premises equipment 130 which has so determined formats information
for transmission during the maintenance action 233, and transmits
that information during the maintenance section 233, so that the
base station controller 120 can receive that information.
[0092] At a step 335, each individual customer premises equipment
130 heading allocations of bandwidth for transmission using
upstream payload elements 223 determines what information that
individual customer premises equipment intends to send to the base
station controller 120. As part of this step, each individual
customer premises equipment 130, intending to send information to
the base station controller 120, formats information into an
upstream payload element 223, and transmits that upstream payload
element 223 during the time assigned for transmission to that
individual cost of premises equipment 130.
[0093] In a preferred embodiment, the base station controller 120
determines, for each time slot possibly allocable for an upstream
payload element 223, which specific individual customer premises
equipment 130 is allocated that particular time slot. However, in
alternative embodiments, the base station controller 120 might
reserve one or more time slots allocable for upstream payload
elements 223 for contention among more than one individual customer
premises equipment 130.
[0094] As noted above, each individual customer premises equipment
130 uses the physical parameters and MAC parameters determined by
the base station controller 120 for that particular customer
premises equipment 130 and transmitted during the map section 221
of the same TDMA frame 210.
[0095] After this step, each individual customer premises equipment
130 has performed one instance of sending information during the
upstream portion 230. The flow point 330 is reached repeatedly and
the steps thereafter are performed repeatedly, for each TDMA frame
210.
[0096] Receiving Upstream Information
[0097] At a flow point 340, preferably reached in parallel with the
flow point 330, the base station controller 120 is ready to receive
information from one or more sets of customer premises equipment
130.
[0098] At a step 341, the base station controller 120 receives
information transmitted during each request section 231 by one or
more individual customer premises equipment 130. As part of this
step, the base station controller 120 determines whether one or
more request sections 231 have been subject to contention (and thus
have been unable to be used to send or receive information). As
part of this step, the base station controller 120 determines what
allocations of bandwidth for transmission it will make for
individual customer premises equipment 130 for the following TDMA
frame 210.
[0099] At a step 342, the base station controller 120 receives
information transmitted during each acknowledgment section 232, by
one or more individual customer premises equipment 130. As part of
this step, the base station controller 120 determines which of its
downstream payload elements 223 sent to individual customer
premises equipment 130 have been acknowledged and therefore have
been received properly.
[0100] At a step 343, the base station controller 120 receives
information transmitted during the maintenance section 233, by one
or more individual customer premises equipment 130. As part of this
step, the base station controller 120 determines any maintenance
steps it must take in response to such information.
[0101] At a step 344, the base station controller 120 receives
information transmitted during one or more upstream payload
elements 223, by one or more individual customer premises equipment
130. As part of this step, similar to receipt of individual request
sections 231 (and possibly similar to receipt of individual
acknowledgment sections 232), the base station controller 120
determines whether one or more upstream payload elements 223 have
been subject to contention (and thus have been unable to be used to
send or receive information).
[0102] In a alternative embodiment, the base station controller 120
parses those upstream payload elements 223 for which it has been
able to receive information, and determines whether those upstream
payload elements 223 include acknowledgments of downstream payload
elements 223 which were sent by the base station controller 122 to
individual customer premises equipment 130. If so, the base station
controller 120 treats those acknowledgments which were
"piggybacked" onto upstream payload elements 223 in similar manner
to acknowledgments received during acknowledgment sections 232.
[0103] As noted above, the base station controller 120 receives and
parses those upstream payload elements 223 using physical
parameters and MAC parameters determined by the base station
controller 120 for that particular customer premises equipment 130
and transmitted during the map section 221 of the same TDMA frame
210.
[0104] After this step, the base station controller 120 has
performed one instance of receiving information during the upstream
portion 230. The flow point 340 is reached repeatedly and the steps
thereafter are performed repeatedly, for each TDMA frame 210.
[0105] An optional step 345 may occur at any time during the method
300 in response to the frequency of dropped packets. A packet is
designated as "dropped" after the method 300 failed to get it
across after re-transmitting it several times. In this step, the
system 100 changes link parameters if two packets are dropped
within a specified number of packet transmissions from each other.
This allows the system 100 to tolerate a certain level of dropped
packets without being affected. However, if the drop rate exceeds a
certain threshold, the link parameters are changed. This approach
is very different from existing methods which change link
parameters in response to explicit measurements such as the
signal-to-interference ratio.
[0106] Generality of the Invention
[0107] The invention has general applicability to various fields of
use, not necessarily related to the services described above. For
example, these fields of use can include one or more of, or some
combination of, the following:
[0108] The invention is applicable to other forms of wireless
communication, such as frequency division multiple access (FDMA) or
code division multiple access (CDMA, also known as spread spectrum
communication);
[0109] The invention is applicable to wireline (that is,
non-wireless) communication, in which now can be achieved from
dynamically adjusting communication parameters, such as physical
parameters or MAC parameters. For example, the invention can be
generalized to wireline communication using modems in which
equalization parameters are to be dynamically adjusted.
[0110] The invention is applicable to other wireless communication
systems, such as satellite communication systems and (microwave
tower or other) point to point transmission systems.
[0111] Other and further applications of the invention in its most
general form, will be clear to those skilled in the art after
perusal of this application, and are within the scope and spirit of
the invention.
[0112] Technical Appendix
[0113] A technical appendix enclosed with this application is part
of the disclosure of this application, and is hereby incorporated
by reference as if fully set forth herein.
[0114] Alternative Embodiments
[0115] Although preferred embodiments are disclosed herein, many
variations are possible which remain within the concept, scope, and
spirit of the invention, and these variations would become clear to
those skilled in the art after perusal of this application.
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