U.S. patent number 9,271,304 [Application Number 14/363,148] was granted by the patent office on 2016-02-23 for method for increasing the address space for mobile terminals in a wireless network.
This patent grant is currently assigned to Telefonaktiebolaget L M Ericsson (publ). The grantee listed for this patent is Hakan Axelsson, Anders Hallberg, Anders Holm, Oskar Myrberg, Jonas Nilsson. Invention is credited to Hakan Axelsson, Anders Hallberg, Anders Holm, Oskar Myrberg, Jonas Nilsson.
United States Patent |
9,271,304 |
Holm , et al. |
February 23, 2016 |
**Please see images for:
( Certificate of Correction ) ** |
Method for increasing the address space for mobile terminals in a
wireless network
Abstract
A method, in a base station subsystem (10), of allocating radio
resources to mobile stations (20) in a wireless communication
system (1) involves the base station subsystem (10) assigning a
respective Temporary Block Flow (TBF) to each mobile station (20)
in a cell (40) in the communication system (1), and then assigning
to each TBF a Temporary Flow Identity (TFI), at least one Packet
Data Channel (PDCH), and an Uplink State Flag (USF) if the TBF is
an uplink TBF. The base station subsystem (10) then selects
different training sequences from a plurality of available training
sequences and assigns a respective different selected training
sequence to two or more TBFs wherein these two or more TBFs share
the same assigned Temporary Flow Identity (TFI), the same assigned
Packet Data Channel (PDCH), and/or the same assigned Uplink State
Flag (USF) if the TBF is an uplink TBF.
Inventors: |
Holm; Anders (Linkoping,
SE), Axelsson; Hakan (Linkoping, SE),
Hallberg; Anders (Vreta Kloster, SE), Myrberg;
Oskar (Norrkoping, SE), Nilsson; Jonas
(Ljungsbro, SE) |
Applicant: |
Name |
City |
State |
Country |
Type |
Holm; Anders
Axelsson; Hakan
Hallberg; Anders
Myrberg; Oskar
Nilsson; Jonas |
Linkoping
Linkoping
Vreta Kloster
Norrkoping
Ljungsbro |
N/A
N/A
N/A
N/A
N/A |
SE
SE
SE
SE
SE |
|
|
Assignee: |
Telefonaktiebolaget L M Ericsson
(publ) (Stockholm, SE)
|
Family
ID: |
48574682 |
Appl.
No.: |
14/363,148 |
Filed: |
December 9, 2011 |
PCT
Filed: |
December 09, 2011 |
PCT No.: |
PCT/SE2011/051496 |
371(c)(1),(2),(4) Date: |
June 05, 2014 |
PCT
Pub. No.: |
WO2013/085446 |
PCT
Pub. Date: |
June 13, 2013 |
Prior Publication Data
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|
|
|
Document
Identifier |
Publication Date |
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US 20150103759 A1 |
Apr 16, 2015 |
|
Current U.S.
Class: |
1/1 |
Current CPC
Class: |
H04W
76/11 (20180201); H04L 5/003 (20130101); H04W
72/1278 (20130101) |
Current International
Class: |
H04W
4/00 (20090101); H04W 72/12 (20090101); H04W
76/02 (20090101); H04L 5/00 (20060101) |
Field of
Search: |
;370/328-329,431
;455/450 |
References Cited
[Referenced By]
U.S. Patent Documents
Foreign Patent Documents
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2420001 |
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May 2011 |
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RU |
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2420890 |
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Jun 2011 |
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RU |
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0251177 |
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Jun 2002 |
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WO |
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2011056118 |
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May 2011 |
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WO |
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2011104371 |
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Sep 2011 |
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WO |
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Other References
Lin, Y., et al., "Two-Stage Dynamic Uplink Channel and Slot
Assignment for GPRS," IEEE International Conference on
Communications, 2001. ICC 2001. Jun. 11-14, 2001. pp. 1335-1339.
vol. 5. Helsinki, Finland. cited by applicant .
Author Unknown, "3GPP TS 43.051 V10.0.0 (Mar. 2011)," 3rd
Generation Partnership Project; Technical Specification Group
GSM/EDGE Radio Access Network; Overall description; Stage 2;
(Release 10). Mar. 2011. pp. 1-65. cited by applicant .
Author Unknown, "Attempt to Progress Discussion on Two Proposed
TBF-Related Features," AT&T; 3GPP TSG GERAN ad hoc; Tdoc
GAHW-00134; Agenda Item 6.1.3; Dec. 11-15, 2000. pp. 1-2. Orlando.
cited by applicant .
Author Unknown, "GERAN IMTC: Discussion on Identifiers," Telefon AB
LM Ericsson; 3GPP TSG GERAN #48; GP-101953; Nov. 22-26, 2010. pp.
1-17. San Jose Del Cabo, Mexico. cited by applicant .
Author Unknown, "GERAN IMTC: Discussion on Extension of the USF
Addressing Space," Telefon AB LM Ericsson, ST-Ericsson SA; 3GPP TSG
GERAN #49; GP-110280; Feb. 28-Mar. 4, 2011. pp. 1-6. Chengdu,
China. cited by applicant .
3GPP, "3rd Generation Partnership Project; Technical Specification
Group GSM/EDGE Radio Access Network; General Packet Radio Service
(GPRS); Mobile Station (MS)--Base Station System (BSS) interface;
Radio Link Control / Medium Access Control (RLC/MAC) protocol
(Release 10)", 3GPP TS 44.060 V10.5.0, Jun. 2011, 1-622. cited by
applicant.
|
Primary Examiner: Tran; Phuc
Attorney, Agent or Firm: Murphy, Bilak & Homiller,
PLLC
Claims
The invention claimed is:
1. A method, in a base station subsystem, of allocating radio
resources to a plurality of mobile stations in a wireless
communication system, the method comprising: the base station
subsystem assigning a respective Temporary Block Flow (TBF) to each
of said plurality of mobile stations in a cell; the base station
subsystem assigning to each said TBF a Temporary Flow Identity
(TFI), at least one Packet Data Channel (PDCH), and an Uplink State
Flag (USF) if the TBF is an uplink TBF; the base station subsystem
selecting different training sequences from a plurality of
available training sequences; and the base station subsystem
assigning a respective different selected training sequence to two
or more TBFs wherein said two or more TBFs share at least one of:
the same assigned Temporary Flow Identity (TFI), the same assigned
Packet Data Channel (PDCH), and the same assigned Uplink State Flag
(USF) if the TBF is an uplink TBF.
2. The method according to claim 1, further comprising: the base
station subsystem arranging said plurality of mobile stations into
a plurality of subsets of mobile stations chosen among the
plurality of mobile stations in a cell; and wherein said step of
assigning training sequences comprises the base station subsystem
assigning a first training sequence to a first TBF assigned to a
mobile station of a first subset of mobile stations, and a second
different training sequence to a second TBF assigned to a mobile
station of a second subset of mobile stations, wherein said first
and second TBF share at least one of: the same assigned Temporary
Flow Identity (TFI), the same assigned Packet Data Channel (PDCH),
and the same assigned Uplink State Flag (USF) if the TBF is an
uplink TBF.
3. The method according to claim 1, wherein said step of assigning
training sequences comprises assigning training sequences
dynamically for each of said plurality of mobile stations in a
cell.
4. The method according to claim 1, further comprising the base
station subsystem scheduling each of said plurality of mobile
stations in a cell for uplink and downlink communication using each
respective training sequence assigned to each respective mobile
station in a cell.
5. The method according to claim 1, further comprising the base
station subsystem transmitting data to each of said plurality of
mobile stations in a cell using each respective training sequence
assigned to each respective mobile station in a cell.
6. The method according to claim 1, wherein the method is
implemented in a General Packet Radio Service/Enhanced Data rates
for GSM Evolution (GPRS/EDGE) mobile network.
7. A base station subsystem configured to allocate radio resources
to a plurality of mobile stations in a wireless communication
system, wherein the base station subsystem comprises: a transmitter
for transmitting to given mobile stations; and one or more
processor circuits operatively associated with the transmitter and
configured to: assign a respective Temporary Block Flow (TBF) to
each of said plurality of mobile stations in a cell; assign to each
said TBF a Temporary Flow Identity (TFI); assign to each said TBF
at least one Packet Data Channel (PDCH); assign for each assigned
uplink PDCH an Uplink State Flag (USF); select different training
sequences from a plurality of available training sequences; and
assign a respective different selected training sequence to two or
more TBFs wherein said two or more TBFs share at least one of: the
same assigned Temporary Flow Identity (TFI), the same assigned
Packet Data Channel (PDCH), and the same assigned Uplink State Flag
(USF) if the TBF is an uplink TBF.
8. The base station subsystem according to claim 7, wherein the one
or more processor circuits are further configured to: arrange said
plurality of mobile stations into a plurality of subsets of mobile
stations chosen among the plurality of mobile stations in a cell;
wherein assign a first training sequence to a first TBF assigned to
a mobile station of a first subset of mobile stations, and a second
different training sequence to a second TBF assigned to a mobile
station of a second subset of mobile stations, wherein said first
and second TBF share at least one of: the same assigned Temporary
Flow Identity (TFI), the same assigned Packet Data Channel (PDCH),
and the same assigned Uplink State Flag (USF) if the TBF is an
uplink TBF.
9. The base station subsystem according to claim 7, wherein the one
or more processor circuits are configured to assign training
sequences dynamically for each of said plurality of mobile stations
in a cell.
10. The base station subsystem according to claim 7, wherein the
one or more processor circuits include a scheduler that is
configured to schedule each of said plurality of mobile stations in
a cell for uplink and downlink communication using each respective
training sequence assigned to each respective mobile station in a
cell.
11. The base station subsystem according to claim 7, wherein the
transmitter is configured to transmit data to each of said
plurality of mobile stations in a cell using each respective
training sequence assigned to each respective mobile station in a
cell.
12. The base station subsystem according to claim 7 configured to
be implemented in a General Packet Radio Service/Enhanced Data
rates for GSM Evolution (GPRS/EDGE) mobile network.
13. A non-transitory computer-readable medium storing a computer
program for allocating radio resources to a plurality of mobile
stations in a wireless communication system, the computer program
comprising code which when run by a processing unit of a base
station subsystem causes the processing unit to: assign a
respective Temporary Block Flow (TBF) to each of said plurality of
mobile stations in a cell; assign to each said TBF a Temporary Flow
Identity (TFI), at least one Packet Data Channel (PDCH), and an
Uplink State Flag (USF) if the TBF is an uplink TBF; select
different training sequences from a plurality of available training
sequences; and assign a respective different selected training
sequence to two or more TBFs wherein said two or more TBFs share at
least one of: the same assigned Temporary Flow Identity (TFI), the
same assigned Packet Data Channel (PDCH), and the same assigned
Uplink State Flag (USF) if the TBF is an uplink TBF.
Description
TECHNICAL FIELD
The present embodiments generally relate to allocating radio
resources for mobile stations in a wireless communication network
and, more particularly, to increasing the addressing space for
mobile stations in such a network.
BACKGROUND
So far, the traffic generated in mobile networks such as e.g. GERAN
(GSM (Global System for Mobile communications) EDGE (Enhanced Data
rates for GSM Evolution) Radio Access Network) and UTRAN (UMTS
(Universal Mobile Telecommunications System) Terrestrial Radio
Access Network) has mostly been dominated by services that require
human interaction, such as e.g. regular speech calls, web surfing,
sending MMS, doing video-chats etc, and the same traffic pattern is
also anticipated for E-UTRAN (Evolved-UTRAN). As a natural
consequence, these mobile networks are designed and optimized
primarily for these "Human Type Communication" (HTC) services.
There is, however, an increasing market segment for Machine Type
Communication (MTC) services, which do not necessarily need human
interaction. MTC services include a very diverse flora of
applications, ranging from e.g. vehicle applications (such as
automatic emergency calls, remote diagnostics and telematics,
vehicle tracking etc.) to gas and power meter readings, and also
network surveillance and cameras, to just give a few examples. The
demands that MTC services put on the mobile network, e.g. in terms
of the number of communication devices to be served in the network,
will without any doubt significantly differ from what is provided
by today's HTC-optimized mobile networks. Thus, in order for mobile
networks such as GERAN and UTRAN to be competitive for these mass
market MTC applications and devices, it is important to optimize
the support of such networks for MTC communication.
One of the critical issues in e.g. GERAN is how to distinguish and
properly address a vast number of devices for the case of
simultaneous data transfer on shared radio resources, since the
available addressing spaces may not be sufficient. One of the
identifiers that may be a bottleneck in this respect is the
so-called Temporary Flow Identity (TFI) which is assigned by the
GERAN network to each Temporary Block Flow (TBF) for the purpose of
e.g. identifying a particular TBF and the transmitted Radio Link
Control/Medium Access Control (RLC/MAC) blocks associated with that
TBF.
In GSM data is sent and received in a time division manner; one
Time Division Multiple Access (TDMA) frame is divided into eight
timeslots. These timeslots can be used for either voice, data or
signaling. To transfer data, a Temporary Block Flow (TBF) needs to
be set up on one or more timeslots, and it is identified by a
Temporary Flow Identity (TFI). Each TBF is assigned a TFI value by
the mobile network. The addressing of the mobile station in
GPRS/EDGE transfer mode is handled by the TA. The uplink and
downlink TFI value is unique per TBF and assigned Packet Data
Channel (PDCH, a timeslot reserved for the packet switched domain).
This limits the number of concurrent TBFs and thus the number of
devices that may share the same radio resources.
In the header of an RLC/MAC block for data transfer, the TFI
identifies the TBF to which the RLC data block belongs. For the
downlink and uplink TFI, the TFI itself is a 5-bit field encoded as
a binary number in the range 0 to 31, which is typically provided
to the mobile station (MS) by the GERAN network upon assignment of
the TBF. This means that, for example, every time an MS receives a
downlink data or control block, it will use the included TFI field
to determine if this block belongs to any (there can be more than
one) of the TBFs associated with that very MS. If so, the block is
obviously intended for this MS, whereupon the corresponding payload
is decoded and delivered to upper layers, and is discarded
otherwise. In the uplink direction the behavior is similar, i.e.
the mobile network uses the TFI value to identify blocks that
belong to the same TBF.
To multiplex mobile stations on the uplink an Uplink State Flag
(USF) is available for each PDCH. The USF field is sent in all
downlink RLC/MAC blocks. When a mobile station reads its own USF
value on a PDCH it is assigned with, it knows that it is allowed to
transmit on that timeslot in the next radio block period. The USF
field is 3 bits in length and 8 different USF values can be
assigned. One USF value normally needs to be reserved for uplink
blocks scheduled by other means than USF, leaving 7 USF values that
can be used for scheduling of UL TBFs.
The numbers of possible TFI values are limited by the available 5
bits, which thus allows for 32 individual values. This may appear
sufficient, and has until now provided no significant limitation.
There are however a number of indicators that the TFI addressing
space may be a limiter in the future.
If a TBF is assigned to be used on more than one PDCH (which is
most often the case) the number of usable TFIs per PDCH drastically
decreases. Assume e.g. that all TBFs are used on all 8 PDCHs. This
means that the average number of TFIs per PDCH will be 32/8=4, as
compared to the 32 TFIs per PDCH that would be the case otherwise.
In most situations it is desirable to spread a TBF over as many
PDCHs as possible in order to improve the statistical multiplexing
gain and flexibility, but this has the drawback of reducing the
potential number of TBFs that can be supported on any given set of
PDCHs.
With recent additions to the 3GPP (3.sup.rd Generation Partnership
Project) standards which allow the use of multiple TBFs associated
with one and the same MS by means of Multiple TBF procedures and/or
Enhanced Multiplexing of a Single TBF (EMST), the number of TBFs
associated with any given MS will no longer be limited to one per
direction. One particular MS could now e.g. in the downlink have
one TBF for a web-surfing session, another for an ongoing voice
call and finally a third for a messaging service such as MSN. The
benefit on splitting these particular services over different TBFs
is of course that they all have different service requirements, but
an obvious drawback is that more TFIs are needed.
The amount of Packet Switched (PS) traffic in a typical GERAN
network is continuously and rapidly increasing already today, with
the usage of classical HTC services as described above. Bearing in
mind the anticipated vast increase in the number of HTC+MTC devices
in the near future, it is more than likely that the PS traffic
volume in GERAN, and implicitly the number of TBFs per transmitter,
will increase manifold. It is not at all an unlikely situation that
for these kinds of services, it would be beneficial to multiplex
perhaps dozens or more users of the same uplink PDCH.
There is therefore a need for a solution for allocating radio
resources for communication devices in a wireless communication
network, such as GERAN, that will increase the number of
communication devices that can be used simultaneously in the
communication network.
SUMMARY
The present disclosure aims to obviate some of the above mentioned
problems, and to provide increased addressing space for mobile
stations in a wireless communication system.
An aspect of the embodiments defines a method, in a base station
subsystem, of allocating radio resources to mobile stations in a
wireless communication system. The method comprises the base
station subsystem assigning a respective Temporary Block Flow (TBF)
to each of the mobile stations in a cell in the communication
system, and then assigning to each TBF a Temporary Flow Identity
(TFI), at least one Packet Data Channel (PDCH), and an Uplink State
Flag (USF) if the TBF is an uplink TBF. The base station subsystem
then selects different training sequences from a plurality of
available training sequences and assigns a respective different
selected training sequence to two or more TBFs wherein these two or
more TBFs share the same assigned Temporary Flow Identity (TFI),
the same assigned Packet Data Channel (PDCH), and/or the same
assigned Uplink State Flag (USF) if the TBF is an uplink TBF.
Another aspect of the embodiments defines a base station subsystem
configured to allocate radio resources to mobile stations in a
wireless communication system. A TBF assigner of the base station
subsystem is configured to assign a respective Temporary Block Flow
(TBF) to each of the mobile stations in a cell in the communication
system. The base station subsystem also comprises a TFI assigner
configured to assign to each TBF a Temporary Flow Identity (TFI), a
PDCH assigner configured to assign to each TBF at least one Packet
Data Channel (PDCH), an USF assigner configured to assign for each
assigned uplink PDCH an Uplink State Flag (USF), a training
sequence selector configured to select different training sequences
from a plurality of available training sequences, and a training
sequence assigner configured to assign a respective different
selected training sequence to two or more TBFs wherein these two or
more TBFs share the same assigned Temporary Flow Identity (TFI),
the same assigned Packet Data Channel (PDCH), and/or the same
assigned Uplink State Flag (USF) if the TBF is an uplink TBF.
A further aspect of the embodiments defines a computer program for
allocating radio resources to mobile stations in a wireless
communication system. The computer program comprises code means
which when run by a processing unit of the base station subsystem
causes the processing unit to assign a respective Temporary Block
Flow (TBF) to each of the mobile stations in a cell in the
communication system, and to assign to each TBF a Temporary Flow
Identity (TFI), at least one Packet Data Channel (PDCH), and an
Uplink State Flag (USF) if the TBF is an uplink TBF. The processing
unit is also caused to select different training sequences from a
plurality of available training sequences, and to assign a
respective different selected training sequence to two or more TBFs
wherein these two or more TBFs share the same assigned Temporary
Flow Identity (TFI), the same assigned Packet Data Channel (PDCH),
and/or the same assigned Uplink State Flag (USF) if the TBF is an
uplink TBF.
An advantage of the disclosed embodiments is that increased
addressing space for mobile stations in a wireless communication
system is provided without impacting the technical specifications
of existing communication systems and the described solution will
thereby work with legacy terminals.
BRIEF DESCRIPTION OF THE DRAWINGS
The embodiments, together with further objects and advantages
thereof, may best be understood by making reference to the
following description taken together with the accompanying
drawings, in which:
FIG. 1 is a schematic illustration of a communication system
according to an embodiment.
FIGS. 2A, 2B and 2C illustrate airframe timeslots on downlink (DL)
and uplink (UL) in a General Packet Radio Service (GPRS)
communication network;
FIG. 3 is a flow chart showing a method for allocating radio
resources for mobile stations according to an embodiment;
FIG. 4 illustrates the message flow between mobile stations and a
base station at Temporary Block Flow (TBF) setup according to an
embodiment;
FIG. 5 is a block diagram of a base station subsystem according to
an embodiment; and
FIG. 6 is a block diagram of a computer implementation according to
an embodiment.
DETAILED DESCRIPTION
The present embodiments generally relate to allocating radio
resources for mobile stations in a communication system and, more
particularly, to increasing the Temporary Flow Identity addressing
space.
Throughout the drawings, the same reference numbers are used for
similar or corresponding elements.
The present disclosure is described in the context of a GPRS/EDGE
wireless communication network. However, the embodiments may also
be implemented in other similar systems.
FIG. 1 is a schematic overview of a portion of a communication
system 1 to which the present embodiments can be applied. The
communication system 1 is preferably a wireless, radio-based
communication network or system providing communication services to
connected user equipment(s) 20. The communication system 1
comprises radio base stations 10 providing communication services
within a coverage area, typically denoted cell 40. Generally,
downlink transmission of user-specific data is performed by the
radio base station 10 on a downlink channel 14 towards the user
equipment 20, whereas uplink data transmission from the user
equipment 20 is performed on an uplink channel 12 in FIG. 1. Some
uplink related control channels are also transmitted by the radio
base stations 10 on the downlink channels 14.
As indicated in the background section, in GSM data is sent and
received in a time division manner; one Time Division Multiple
Access (TDMA) frame (5 ms) is divided into eight timeslots, usually
numbered 0 to 7 from "left to right" in time. These timeslots can
be used for either voice, data or signaling. Since most mobile
stations cannot send and receive at the same time, they have to
switch between sending and receiving. For this reason the uplink
(UL) is shifted 3 timeslots "to the right" in time, as illustrated
in FIGS. 2A-C, so a mobile station can send and receive on the
"same" timeslot.
To transfer data, a Temporary Block Flow (TBF) needs to be set up
on one or more timeslots, and it is identified by a Temporary Flow
Identity (TFI). Each TBF is assigned a TFI value by the mobile
network. The addressing of the mobile station in GPRS/EDGE transfer
mode is handled by the TFI. The uplink and downlink TFI value is
unique per TBF and assigned Packet Data Channel (PDCH, a timeslot
reserved for the packet switched domain). To multiplex mobile
stations on the uplink an Uplink State Flag (USF) is available for
each PDCH. The USF field is sent in all downlink RLC/MAC blocks.
When a mobile station reads its own USF value on a PDCH it is
assigned with, it knows that it is allowed to transmit on that
timeslot in the next radio block period.
In the example shown in FIG. 2A, timeslots 4-7 are dedicated for
data. A mobile station is reserved on timeslot 4-7 in the downlink
(DL) and 6 in the uplink (UL) (illustrated with a dotted pattern).
The downlink TFI for that mobile station is denoted TFI X, the
uplink USF is denoted USF X and the uplink TFI is denoted TFI
Y.
In FIG. 2B another mobile station enters the network, and the
system allocates timeslots 4-7 in the downlink and 7 in the uplink
(illustrated with a sparser dotted pattern for the new mobile). The
downlink TFI for that mobile station is denoted TFI 1, the uplink
USF is denoted USF 1 and the uplink TFI is denoted TFI 2. So far in
this example, two TFIs have been used on each allocated timeslot on
the downlink, and one USF on timeslot 6 and one USF on timeslot 7
have been used on the uplink.
In FIG. 2C more mobile stations enter the network and more
resources are occupied. The examples in FIGS. 2A-C illustrate how
users could be reserved on timeslots in the Packet Switched (PS)
domain; it might or might not reflect an actual scenario.
For the downlink and uplink TFI, the TFI itself is a 5-bit field.
The numbers of possible TFI values are thus limited by the
available 5 bits, which allows for 32 individual values in the
range 0 to 31. The USF field is 3 bits in length and 8 different
USF values can be assigned. One USF value normally needs to be
reserved for uplink blocks scheduled by other means than USF,
leaving 7 USF values that can be used for scheduling of UL
TBFs.
Thus, problems with the existing solutions are: Maximum 7 uplink
TBFs can share the same PDCH due to USF value range. A TBF is
assigned one and only one TFI and the TFI must be unique per PDCH.
The maximum number of TBFs sharing one PDCH is 32. For the example
with TBFs using 8 timeslots the maximum number of TBFs will be 32
on a carrier.
The above means that the address space of USF and TFI is too small
for the expected PS traffic growth, as indicated in the background
section.
The patents US 2011/0194419 and WO 2011/056118 both address this
issue, using basically the same approach for increasing the address
space when assigning addresses to a communication device, i.e. they
both make use of an extended addressing individual (extended
TFI/extended USF) for increasing the address space. In order for
this approach to work, transmission of parallel radio bursts is
needed, which the mobile stations shall combine into this extended
addressing individual. This requires double decoding and
interference cancellation techniques similar to VAMOS (Voice
services over Adaptive Multi-user channels on One Slot). This means
that transmitted radio blocks are restricted to GMSK (Gaussian
Minimum Shift Keying) modulation, i.e. any higher order modulations
cannot be used with this technique. Also, the technique described
in these patents requires standard changes and support for new
mobile stations.
The basic concept of the embodiments described herein is to
increase the address space for the TBFs sharing the same resources
without impacting the technical specifications of existing
communication systems and this will thereby work with legacy
terminals.
The inventors of the present disclosure have identified the
possibility, and usefulness, of providing more than one training
sequence and assigning different training sequences to different
TBFs. Thereby, each carrier will have multiple training sequences
defined. For each training sequence a full set of USF and TFI value
ranges will be available. This increases the address space for the
carrier with a multiple of the number of training sequences defined
for the carrier. Note that the disclosed solution requires that the
Radio Resource Management algorithm for TBF assignment is extended
with an algorithm to select training sequence in combination with
USF and TFI.
With the present embodiments it will be possible to re-use the USF
and TFI addresses within the same POCH by using different training
sequences for different mobile stations on the same PDCH. Until
now, the USF and TFI addresses can only be used once per PDCH, but
with the present embodiments the USF and TR addresses can be used
once per training sequence and PDCH.
According to a basic embodiment, at TBF assignment the mobile
station is assigned not only USF, TFI and PDCH(s), as in prior art,
but also a training sequence. The USF and TFI need to be unique
within a PDCH and training sequence, so an algorithm is needed in
the network to decide what USF, TFI, PDCH(s) and training sequence
should be assigned to the mobile station. In other words, mobile
stations can share identical or near identical sets of PDCH, TFI
and USF by being assigned different training sequences.
FIG. 3 is a flow chart illustrating a method for allocating radio
resources for a plurality of mobile stations according to an
embodiment. According to the method, the base station subsystem 10
assigns a TBF to each mobile station 20 in a cell 40, and then
assigns a TFI, one or more PDCH(s) and, if the TBF is an uplink
TBF, also an USF, to each assigned TBF. The base station subsystem
10 then selects a number of training sequences and assigns
different training sequences to each of the mobile stations 20 in
the cell 40. The mobile stations 20 may all share the same TFI,
PDCH and/or USF, as long as they have different training sequences.
The combination of training sequence, TFI, PDCH and/or USF must
however be unique.
Thus, the method illustrated in FIG. 3 generally starts in step S10
where the base station subsystem 10 assigns a respective TBF to
each of the mobile stations 20 in a cell 40. In a next step S20,
the base station subsystem 10 assigns each TBF with a TFI, at least
one PDCH, and an USF if the TBF is an uplink TBF. In a next step
S30, the base station subsystem 10 selects different training
sequences from a plurality of available training sequences.
Finally, in a step S40, the base station subsystem 10 assigns a
respective different selected training sequence to two or more
TBFs, wherein the two or more TBFs share the same assigned TFI,
PDCH, and/or USF if the TBF is an uplink TBF. This means that it
will be possible to re-use the TFI and USF values within the same
PDCH by using different training sequences for different mobiles on
the same PDCH. Thus, the address space for the carrier will
increase with a multiple of the number of training sequences as
compared to prior art. The method generally ends after step
S40.
It is desired that the assigned training sequence can be
dynamically changed for each mobile station 20, as the TR and USF
already can before this disclosure. In a particular embodiment,
step S40 of FIG. 3 comprises the base station subsystem 10
assigning training sequences dynamically for each of the mobile
stations 20 in a cell 40. This can be accomplished by re-assigning
the TBF with a control message. In prior art, the TFI and USF can
already be dynamically changed in this manner. Hence, it should be
possible to use the already existing TBF re-assigning control
message also for implementing dynamical assigning of training
sequences according to the present embodiments.
In an alternative embodiment, the mobile stations 20 in a cell 40
are arranged into subsets 30. Arranging the mobile stations 20 into
subsets 30 can be done in several ways according to vendor
implementation. They could e.g. be divided between subsets based on
Quality of Service (QoS) requirements, subscriber group or
randomly. In this embodiment, different training sequences are used
for different subsets 30 of mobile stations 20 in a cell 40. Thus,
the same training sequence is used for all mobile stations 20
within a subset 30. Obviously, the mobile stations 20 within a
subset 30 need to be assigned with a unique combination of TFI,
PDCH and/or USF, whereas mobile stations 20 belonging to different
subsets 30 can still share the same TFI, PDCH and/or USF:
This alternative embodiment comprises an optional additional step
S35, illustrated with a dotted line in FIG. 3 to indicate that it
is optional, and preceding the step S40 of the method of FIG. 3. In
step S35 the base station subsystem 10 arranges the mobile stations
20 into a plurality of subsets 30 of mobile stations 20 chosen
among the mobile stations 20 in a cell 40. Then, in the next step
S40 when different training sequences are assigned, the base
station subsystem 10 assigns a first training sequence to a first
TBF assigned to a mobile station 20 of a first subset 30 of mobile
stations 20, and a second different training sequence to a second
TBF assigned to a mobile station 20 of a second subset 30 of mobile
stations 20, wherein the first and second TBF share the same
assigned TFI, PDCH, and/or USF if the TBF is an uplink TBF. This
means that when performing step S40, the base station subsystem 10
will assign the same training sequence for all mobiles in the
entire subset 30, and use different TFI, PDCH and USF within the
subset. In prior art communication networks, the same training
sequence is used for all mobiles in an entire cell 40, whereas in
the embodiments described herein, the same training sequence is
used for all mobiles in a subset 30 of mobiles 20 in a cell 40.
This basically means that the same amount of mobile stations 20 can
be assigned in a subset 30 when using the technique according to
the present embodiments, as in a cell 40 when using technique
according to prior art.
When the network shall uplink-schedule a mobile station 20, it
transmits the assigned USF using the assigned training sequence.
Any other mobile station 20 with the same USF assigned will not
successfully decode this USF, since it will use another training
sequence to try to decode the block, and will therefore not be
uplink-scheduled. In an optional additional step S50 of the method
illustrated in FIG. 3, the base station subsystem 10 schedules each
of the mobile stations 20 in a cell 40 for uplink and downlink
communication using each respective training sequence assigned to
each respective mobile station 20 in a cell 40.
When the network shall transmit a downlink block to a mobile
station 20 it shall transmit it using the training sequence which
was assigned to the mobile station 20 at TBF assignment together
with the assigned TFI. This will make sure that only one mobile
station 20 will successfully receive the downlink block. In an
optional additional step S60 of the method illustrated in FIG. 3,
the base station subsystem 10 transmits data to each of the mobile
stations 20 in a cell 40 using each respective training sequence
assigned to each respective mobile station 20 in a cell 40.
The method illustrated in FIG. 3 is preferably implemented in a
General Packet Radio Service/Enhanced Data rates for GSM Evolution
(GPRS/EDGE) mobile network.
FIG. 4 shows an example of the message flow between mobile stations
(MS) and a base station at TBF setup with multiple training
sequences according to an embodiment. The message flow according to
this example is as follows: 1. Channel Request: The MS performs
access on Random Access Channel (RACH). 2. Immediate Assignment:
The network assigns the MS with an index to a certain training
sequence (TS) and a channel together with a USF. 3. Uplink
Scheduling to MS 1: To schedule the MS for uplink transmission the
network sends downlink data to any MS. The header also contains the
USF value for the MS that should be scheduled in the next radio
block period. Another MS with a different TS will not be able to
decode the header with the USF value and will thus not send. 4.
Uplink Transfer from MS 1: The MS that was scheduled will transfer
its uplink data. 5. Uplink Scheduling to MS 2: The network now
schedules the same USF to another MS, but using a different TS. 6.
Uplink Transfer from MS 2: The MS that was scheduled will transfer
its uplink data. 7. Downlink data to MS 1: The network now sends
data to one MS. The MS with the correct combination of TS and TFI
will use the data. 8. Downlink data to MS 2: The network now sends
data to another MS with the same TFI as the previous one but with a
different TS. 9. Packet Timeslot Reconfigure to MS 1: The network
can change the training sequence that should be used by sending a
Packet Timeslot Reconfigure, changing both uplink and downlink
TBF.
Note that the message flow described in FIG. 4 is just an example
and other scenarios are possible within the scope of the
embodiments described herein.
With reference to FIG. 5, an embodiment of a base station subsystem
10 suitable for providing the functionality of the method described
in connection with FIG. 3 will be described below. FIG. 5 is a
schematic block diagram of a base station subsystem 10 according to
an embodiment. The base station subsystem 10 is configured to
allocate radio resources to a plurality of mobile stations 20 in a
wireless communication system 1.
According to one embodiment, the base station subsystem 10
comprises a TBF assigner 110 configured to assign a respective TBF
to each of the mobile stations 20 in a cell 40, a TFI assigner 120
configured to assign to each TBF a TFI, a PDCH assigner 130
configured to assign to each TBF at least one PDCH, an USF assigner
140 configured to assign for each assigned uplink PDCH an USF, a
training sequence selector 150 configured to select different
training sequences from a plurality of available training
sequences, and a training sequence assigner 160 configured to
assign a respective different selected training sequence to two or
more TBFs, wherein the two or more TBFs share the same assigned
TFI, PDCH, and/or USF if the TBF is an uplink TBF.
In a particular embodiment, the training sequence assigner 160 is
configured to assign training sequences dynamically for each of the
mobile stations 20 in a cell 40. This can be accomplished by
configuring the training sequence assigner 160 to re-assign the TBF
with a control message. In prior art, the TFI and USF can already
be dynamically changed in this manner. Hence, it should be possible
to use the already existing TBF re-assigning control message also
for implementing dynamical assigning of training sequences
according to the present embodiments.
In another embodiment, the base station subsystem 10 further
comprises a mobile station arranger 170 configured to arrange the
mobile stations 20 into a plurality of subsets 30 of mobile
stations 20 chosen among the mobile stations 20 in a cell 40. In
this embodiment, the training sequence assigner 160 is configured
to assign a first training sequence to a first TBF assigned to a
mobile station 20 of a first subset 30 of mobile stations 20, and a
second different training sequence to a second TBF assigned to a
mobile station 20 of a second subset 30 of mobile stations 20,
wherein the first and second TBF share the same assigned TFI, PDCH,
and/or USF if the TBF is an uplink TBF. This means that the
training sequence assigner 160 is configured to assign the same
training sequence for all mobiles in the entire subset 30, and use
different TFI, PDCH and USF within the subset. In prior art
communication networks, the same training sequence is used for all
mobiles in an entire cell 40, whereas in the embodiments described
herein, the same training sequence is used for all mobiles in a
subset 30 of mobiles 20 in a cell 40. This basically means that the
same amount of mobile stations 20 can be assigned in a subset 30
when using the technique according to the present embodiments, as
in a cell 40 when using technique according to prior art.
In a further embodiment, the base station subsystem 10 further
comprises a scheduler 180 configured to schedule each of the mobile
stations 20 in a cell 40 for uplink and downlink communication
using each respective training sequence assigned to each respective
mobile station 20 in a cell 40. For example, when the network shall
uplink-schedule a mobile station 20, the scheduler 180 transmits
the assigned USF using the assigned training sequence. Any other
mobile station 20 with the same USF assigned will not successfully
decode this USF, since it will use another training sequence to try
to decode the block, and will therefore not be
uplink-scheduled.
In yet another embodiment, the base station subsystem 10 further
comprises a transmitter 190 configured to transmit data to each of
the mobile stations 20 in a cell 40 using each respective training
sequence assigned to each respective mobile station 20 in a cell
40. When the network shall transmit a downlink block to a mobile
station 20 the transmitter 190 shall transmit it using the training
sequence which was assigned to the mobile station 20 at TBF
assignment together with the assigned TFI. This will make sure that
only one mobile station 20 will successfully receive the downlink
block.
In a particular embodiment, the base station subsystem 10 is
configured to be implemented in a General Packet Radio
Service/Enhanced Data rates for GSM Evolution (GPRS/EDGE) mobile
network.
The units 110-190 of the base station subsystem 10 can be
implemented in hardware, in software or a combination of hardware
and software. Although the respective units 110-190 disclosed in
conjunction with FIG. 5 have been disclosed as physically separate
units 110-190 in the base station subsystem 10, and all may be
special purpose circuits, such as ASICs (Application Specific
Integrated Circuits), alternative embodiments are possible where
some or all of the units 110-190 are implemented as computer
program modules running on a general purpose processor.
In such a case and with reference to FIG. 6, the base station
subsystem 10 can be implemented in a computer 200 comprising a
general input/output (I/O) unit 210 in order to enable
communication in the network, a processing unit 220, such as a DSP
(Digital Signal Processor) or CPU (Central Processing Unit). The
processing unit 220 can be a single unit or a plurality of units
for performing different steps of the method described herein. The
computer 200 also comprises at least one computer program product
230 in the form of a non-volatile memory, for instance an EEPROM
(Electrically Erasable Programmable Read-Only Memory), a flash
memory or a disk drive. The computer program product 230 comprises
computer readable code means and a computer program 240 for
allocating radio resources to a plurality of mobile stations 20 in
a wireless communication system 1.
The computer program 240 comprises code means 241-244 which when
run by a processing unit 220 of the base station subsystem 10,
causes the processing unit 220 to perform the steps of the method
described in the foregoing in connection with FIG. 3. Hence, in an
embodiment the code means 241-244 in the computer program 240
comprises an assigning TBF module for assigning a TBF value to each
of the mobile stations 20 in a cell 40, an assigning TFI, PDCH, USF
module for assigning to each TBF a TFI, at least one PDCH and an
USF if the TBF is an uplink TBF, a selecting TS module for
selecting different training sequence from a plurality of available
training sequences, and an assigning TS module for assigning a
respective different selected training sequence to two or more TBFs
wherein the two or more TBFs share the same assigned TFI, PDCH
and/or USF if the TBF is an uplink TBF.
The embodiments as disclosed herein can be used to increase the
address space of a wireless communication system, such as the
GPRS/EGDE mobile network, allowing more users sharing the same
PDCHs on the air interface. This allows for higher utilization of
the available spectrum on the air interface which is beneficial to
the operator Capital expenditures (CAPEX). It also decreases the
need to fast disconnect TBFs to free up addressing resources which
is beneficial to the end user experience.
This solution does not require any change in technical
specifications and will therefore work with all legacy GPRS/EDGE
capable mobile devices.
The embodiments described above are to be understood as a few
illustrative examples of the present invention. It will be
understood by those skilled in the art that various modifications,
combinations and changes may be made to the embodiments without
departing from the scope of the present invention. In particular,
different part solutions in the different embodiments can be
combined in other configurations, where technically possible. The
scope of the present invention is, however, defined by the appended
claims.
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