U.S. patent application number 13/527169 was filed with the patent office on 2012-10-11 for communication apparatus, communication method and program.
This patent application is currently assigned to NTT DOCOMO, INC.. Invention is credited to Sadayuki Abeta, Atsushi Harada, Anil Umesh.
Application Number | 20120257493 13/527169 |
Document ID | / |
Family ID | 38218066 |
Filed Date | 2012-10-11 |
United States Patent
Application |
20120257493 |
Kind Code |
A1 |
Umesh; Anil ; et
al. |
October 11, 2012 |
COMMUNICATION APPARATUS, COMMUNICATION METHOD AND PROGRAM
Abstract
A communication apparatus includes an error detection unit
conducting error detection on N packet data units received in N
transmission processes; a first transmission unit transmitting an
affirmative response signal or a first retransmission request
signal depending on a result of the error detection; a storage unit
storing an affirmatively responding packet for forwarding to an
upper layer; a second transmission unit, if affirmatively
responding packets are not consecutive, determining whether a
missing packet must be retransmitted and transmitting a second
retransmission request signal; and a forwarding unit reordering the
packet data units and forwarding the packets in the storage unit to
the upper layer.
Inventors: |
Umesh; Anil; (Yokohama-shi,
JP) ; Harada; Atsushi; (Kawasaki-shi, JP) ;
Abeta; Sadayuki; (Yokohama-shi, JP) |
Assignee: |
NTT DOCOMO, INC.
Tokyo
JP
|
Family ID: |
38218066 |
Appl. No.: |
13/527169 |
Filed: |
June 19, 2012 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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12159072 |
Sep 22, 2008 |
8214709 |
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PCT/JP2006/325977 |
Dec 26, 2006 |
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13527169 |
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Current U.S.
Class: |
370/216 |
Current CPC
Class: |
H04L 1/1812 20130101;
H04L 1/1822 20130101; H04L 1/1854 20130101; H04L 69/326 20130101;
H04L 1/1832 20130101; H04L 1/1803 20130101; H04L 1/1841 20130101;
H04L 1/1642 20130101 |
Class at
Publication: |
370/216 |
International
Class: |
H04L 29/14 20060101
H04L029/14; H04L 12/26 20060101 H04L012/26; H04L 12/24 20060101
H04L012/24 |
Foreign Application Data
Date |
Code |
Application Number |
Dec 28, 2005 |
JP |
2005-379990 |
Claims
1. A communication apparatus for receiving data in accordance with
an N process SAW based hybrid ARQ method, comprising: an error
detection unit conducting error detection on N packet data units
received in N transmission processes; a first transmission unit
transmitting an affirmative response signal or a first
retransmission request signal depending on a result of the error
detection; a storage unit storing an affirmatively responding
packet for forwarding to an upper layer; a second transmission
unit, if affirmatively responding packets are not consecutive,
determining whether a missing packet must be retransmitted and
transmitting a second retransmission request signal; and a
forwarding unit reordering the packet data units and forwarding the
packets in the storage unit to the upper layer.
2. The communication apparatus as claimed in claim 1, wherein the
second retransmission request signal is generated if a
retransmission process for the missing packet is not being carried
out or if an error is detected in the missing packet even after
completion of the retransmission process for the missing
packet.
3. The communication apparatus as claimed in claim 1, wherein the
order of packets is determined with identification numbers assigned
to the respective packet data units.
4. A method of receiving data in accordance with an N process SAW
based hybrid ARQ method, comprising the steps of: conducting error
detection on N packet data units received in N transmission
processes; transmitting an affirmative response signal or a first
retransmission request signal depending on a result of the error
detection; storing an affirmatively responding packet for
forwarding to an upper layer and determining order of the packets;
if the determined order is not consecutive, determining whether a
missing packet must be retransmitted and transmitting a second
retransmission request signal; and reordering the packet data units
and forwarding the packets in the storage unit to the upper
layer.
5. The method as claimed in claim 4, wherein the second
retransmission request signal is generated if a retransmission
process for the missing packet is not being carried out or if an
error is detected in the missing packet even after completion of
the retransmission process for the missing packet.
6. A program causing a communication apparatus to receive data in
accordance with an N process SAW based hybrid ARQ method,
comprising the steps of: conducting error detection on N packet
data units received in N transmission processes; transmitting an
affirmative response signal or a first retransmission request
signal depending on a result of the error detection; storing an
affirmatively responding packet for forwarding to an upper layer
and determining order of the packets; if the determined order is
not consecutive, determining whether a missing packet must be
retransmitted and transmitting a second retransmission request
signal; and reordering the packet data units and forwarding the
packets in the storage unit to the upper layer.
7. The program as claimed in claim 6, wherein the second
retransmission request signal is generated if a retransmission
process for the missing packet is not being carried out or if an
error is detected in the missing packet even after completion of
the retransmission process for the missing packet.
Description
TECHNICAL FIELD
[0001] The present invention relates to the technical field of
mobile communications, and more particularly relates to a
communication apparatus, method and program for communicating
packets by issuing Hybrid Automatic Repeat reQuests (HARQ).
BACKGROUND ART
[0002] In this technical field, Automatic Repeat reQuest (ARQ)
method is utilized for improved communication reliability. In the
ARQ method, received packets are subjected to error detection, and
the transmitter side is requested to retransmit packets including
unacceptably significant errors. The error detection may be
conducted in accordance with any existing technique such as CRC
(Cyclic Redundancy Check) scheme. In response to receipt of the
request, the transmitter side retransmits the requested packets. As
a result, it is possible to partially prevent an application in the
receiver side from running without any packet.
[0003] FIG. 1 shows an exemplary operation of the ARQ method. For
example, Internet Protocol (IP) based packets A, B, C, . . . are
received from an upper apparatus and stored in a reception buffer
in abase station in the order (S1). The received IP packet is
divided into fixed length blocks for transmission in a lower layer
(S2). Then, radio transmission of a predefined number of blocks is
sequentially carried out via physical channels, and the blocks are
received at a mobile station (S3). In the illustrated example, two
blocks are transmitted in each transmission time interval (TTI).
The mobile station conducts error detection on the received
packets. The received packets are stored in a RLC (reception)
buffer in the mobile station (S4). In this case, retransmission
requests for error detected packets are transmitted to the base
station. In the illustrated example, errors are detected for the
11th and 12th blocks as illustrated in "NG", and the mobile station
requests the base station to retransmit the blocks. The mobile
station forwards error free packets to layers above the RLC such as
an application layer (S5). A packet including the detected error,
which corresponds to packet C in the illustration, is discarded,
and then the mobile station waits for an appropriate packet and
after completion of the retransmission procedure, forwards the
retransmitted packet to an upper layer.
[0004] For further improvement in the communications reliability, a
Hybrid ARQ (HARQ) scheme resulting from the error correction scheme
being combined with the ARQ scheme is proposed. This may be also
employed in the HSDPA (High Speed Downlink Packet Access)
scheme.
[0005] FIG. 2 is a schematic block diagram illustrating a base
station and a mobile station in accordance with the HARQ scheme,
and FIG. 3 shows an exemplary operation of the HARQ scheme. IP
packets A, B, C, . . . are received from an upper apparatus and
stored in an RLC/ARQ or reception buffer (FIG. 2) in a base station
in order (S1 in FIG. 3). The received IP packets are divided into
fixed length blocks in the RLC buffer in FIG. 2 (S2). Then, one or
more fixed length blocks are bundled and transmitted in an HARQ-PDU
processing unit depending on the radio environment. The individual
blocks are identified with the sequence number (SN=1, 2, . . . ).
The IP packets are radio transmitted via physical channels in unit
of a predefined number of blocks and are received in a mobile
station (S3). Packet data units including one or more blocks are
assigned the respective numbers (TSN=1, 2, . . . ) and processes
for transmitting information items specified by the numbers are
assigned process numbers (P1, P2, . . . ). The mobile station
performs error detection on the received packets, and if an error
is detected as illustrated in "NG", the mobile station requests the
base station to retransmit the associated packet. The received
packets are stored in a reordering buffer illustrated in FIG. 2
(S4). The reordering buffer holds packets not being in need of
retransmission until missing packets are received. In the
illustrated example, an error is detected for a packet data unit
corresponding to TSN=2 (whose process number is P2), and the mobile
station requests the base station to retransmit it. In response,
the base station conducts retransmission. In the illustrated
example, the retransmitted packets are received without any error
and stored in the reordering buffer. At this stage, the
retransmission requests are carried out in a MAC sublayer. The
stored packets are reordered in the reordering buffer in order of
the TSN number. The properly reordered packets are decomposed into
packet data units (RLC-PDUs) in the RLC layer and then stored in
the RLC buffer (S5). It is determined whether the packets stored in
the RLC buffer are also continuous in terms of the sequence number
SN. The determination is made because in an exemplary case of an
error still being detected even after the maximum retransmission
times are reached in the HARQ, a missing packet may still be
detected in a packet in the RLC buffer. In such a case,
retransmission in the RLC layer is requested by the mobile station
to the base station. At this stage, the retransmission request
operations are carried out in the RLC layer (also referred to as an
ARQ layer). The mobile station forwards error free packets to an
upper layer such as an application layer from the RLC. For packets
including error detected blocks, the mobile station waits for an
appropriate packet and after completion of the retransmission
procedure, forwards the retransmitted packets to the upper layer
(S6). The above-mentioned conventional ARQ and HARQ methods are
described in non-patent document 1 publicly disclosed at the filing
date of the base priority application of the present
application.
[0006] Non-patent document 1: 3GPP TS 25.301 6.4.0, Internet
<URL: http://www.3gpp.org>
DISCLOSURE OF INVENTION
Problem to be Solved by the Invention
[0007] Since the sequence number SN for specifying packet data
units in the RLC layer and the number TSN for specifying packet
data units in the MAC layer are represented with fixed numbers of
bits, these numbers are cyclically assigned to the packets. For
example, if the sequence number SN is represented with 12 bits,
2.sup.12=4,096 numbers are cyclically used. For this reason, in the
case of a single number being assigned to each transmitted packet,
the receiver side cannot determine without difficulty whether the
received packet belongs to the current cycle or the previous
cycle.
[0008] In order to eliminate such inconvenience, some technique
referred to as transmission stalling is conventionally used. In
this technique, without confirmation response from the receiver
side, the number of continuously transmittable packet data units is
limited in the transmitter side. Specifically, 2,048 packets
following the packet of SN=i, that is, the packets of SN (i+1)
through (i+2049), may be continuously transmitted after
transmission of the packet of SN=i while the SN (i+2050) and
subsequent packets are prevented from being transmitted until ACK
(confirmation response or affirmative response) is obtained. Once
the transmitter obtains the confirmation response for the packet of
SN=i, 2,048 packets of SN=(i+2) through (i+2051) may be transmitted
after transmission of the packet of SN=(1+1) without confirmation
response of the packet of SN=i+1. The number or size of packets
transmittable without confirmation response is referred to as a
transmission window. Each time a confirmation response is
consecutively obtained, the range of the transmission window is
incrementally shifted in the increasing direction of the SN. On the
other hand, if a confirmation response is not consecutively
obtained, the range of the transmission window is not shifted. By
limiting the number of packets transmittable without confirmation
response to half of the maximum of numbers that can be represented,
the receiver can determine whether received packets are
retransmitted ones. Such a scheme is also referred to as Stop And
Wait (SAW) scheme.
[0009] As stated above, the retransmission operations are carried
out in both the MAC layer and the RLC layer. In any of the layers,
the packet data units are specified with a fixed number of bits,
and thus the transmission stalling may be carried out in the
retransmission operations in both layers. However, the packet data
units have different sizes in the MAC layer and the RLC layer, and
the reception timings of confirmation responses (ACKs) after data
transmission may differ from each other in the MAC layer and the
RLC layer. As a result, the transmission window has different sizes
in the layers. In general, confirmation responses may be more
quickly obtained in the MAC layer than the RLC layer. For example,
the size of the transmission window for retransmission request
operations in the RLC layer can be set to be 2,048, and the size of
the transmission window in the MAC layer can be set to be 16. It is
assumed that the maximum number of the TSN is equal to 32.
[0010] However, if the transmission stalling is carried out
separately in the MAC layer and the RLC layer, the transmitter can
transmit only packets belonging to both transmission windows. In
other words, even if data belongs to one of the transmission
windows, if it is not within the range of the other transmission
window, transmission of the data is prevented. FIG. 4 shows
separate operations of the transmission stalling. In the
illustrated example, it is assumed that confirmation responses have
been already obtained for the packets of SN=1, 2, while no
confirmation response has been obtained for the packet of SN=3. At
this time point, the packets of SN=4 through 2051 following the
packet of SN=3 may be continuously transmitted, while the packet of
SN=2052 and the subsequent packets are prevented from being
transmitted. On the other hand, in the illustrated example, the
packet of SN=3 is included in the packet data unit of TSN=13. Thus,
according to the transmission stalling in the MAC layer, the
packets of TSN=14 through 29 following the packet of TSN=13 may be
continuously transmitted, while the packet of TSN=30 and the
subsequent packets are prevented from being transmitted. As a
result, the packets of SN=3 through 918 may be continuously
transmitted, while the packet of SN=919 and the subsequent packets
are prevented from being transmitted. In this manner, according to
the conventional scheme, the transmitter side can transmit only
packets belonging to both transmission windows, which may be
disadvantageous from the viewpoint of improved throughput.
[0011] One object of the present invention is to provide a
communication apparatus, a retransmission control method and a
program for forwarding packets appropriately and quickly in a
communication system in accordance with N process SAW based
retransmission control.
Means for Solving the Problem
[0012] In the present invention, a communication apparatus for
receiving data in accordance with N process SAW (Stop And Wait)
based hybrid ARQ method is used. The communication apparatus
includes an error detection unit conducting error detection on N
packet data units received in N transmission processes; a first
transmission unit transmitting an affirmative response signal or a
first retransmission request signal depending on a result of the
error detection; a storage unit storing an affirmatively responding
packet for forwarding to an upper layer; a second transmission
unit, if affirmatively responding packets are not consecutive,
determining whether a missing packet must be retransmitted and
transmitting a second retransmission request signal; and a
forwarding unit reordering the packet data units and forwarding the
packets in the storage unit to the upper layer.
Advantage of the Invention
[0013] According to the embodiments of the present invention,
packets can be appropriately and quickly transmitted in a
communication system in accordance with N process SAW based
retransmission control.
BRIEF DESCRIPTION OF DRAWINGS
[0014] FIG. 1 shows a conventional retransmission operation;
[0015] FIG. 2 shows a schematic functional block diagram of a
conventional base station and a conventional mobile station;
[0016] FIG. 3 shows a conventional retransmission operation;
[0017] FIG. 4 is a diagram for explaining a problem of a
conventional retransmission operation;
[0018] FIG. 5A shows a conventional protocol hierarchy;
[0019] FIG. 5B shows a protocol hierarchy according to the present
invention;
[0020] FIG. 6 shows a schematic functional block diagram
illustrating a base station and a mobile station according to one
embodiment of the present invention;
[0021] FIG. 7 shows a retransmission operation according to one
embodiment of the present invention; and
[0022] FIG. 8 is a flowchart of a retransmission request operation
according to one embodiment of the present invention.
LIST OF REFERENCE SYMBOLS
[0023] UE: user equipment
[0024] ARQ: automatic retransmission request
[0025] HARQ: hybrid automatic retransmission request
[0026] PDU: packet data unit
[0027] RLC: radio link control
[0028] MAC: media access control
BEST MODE FOR CARRYING OUT THE INVENTION
[0029] Hereinafter, the present invention will be described from
the viewpoint of protocol hierarchy. Conventional protocol
hierarchy will be also described for comparison.
[0030] FIG. 5A shows an exemplary layer model for conventional
techniques as illustrated in FIGS. 2 and 3. As stated above,
received packets are subjected to error detection in the layer
1/MAC layer, and in response to error detection (or detection of
significant errors exceeding acceptable level) as indicated in
CRC-NG in the illustration, retransmission of the error packet is
requested. In the RLC/ARQ layer, it is determined whether the
sequence numbers SNs are consecutive, and if it is detected that a
certain sequence number is missing, retransmission of the packet is
requested. Data transmission from the MAC layer to the RLC/ARQ
layer is carried out under conditions where the packet order is
conserved. Operations for arranging the order are carried out in a
reordering buffer. Transmission of packets to an upper layer under
conditions of the order being arranged is referred to as In
Sequence Delivery (ISD). Also, data transmission of packets from
the RLC/ARQ layer to an upper layer (an application layer or a PDCP
layer in the illustration) is carried out in accordance with ISD.
In the RLC layer, the sequence number SN is monitored, and if it is
detected that a certain sequence number is missing, the
retransmission is carried out to maintain the packet order in the
RLC reception buffer.
[0031] This scheme may be preferable from the viewpoint of reliable
arrangement of the data order. However, since two transmission
stalling operations are separately carried out by using different
transmission windows, the throughput may be degraded as stated
above. On the other hand, the essential purpose of the
retransmission is to supply a series of consecutive packets without
any missing packet to an application layer and/or others. Thus, it
may not be a requirement to fulfill respective ISDs in the two
separate transmission stalling operations. The present invention
can conserve the order of packets forwarded to an upper layer
without the duplicated transmission stalling operations through
improved triggering of retransmission requests.
[0032] FIG. 5B shows an exemplary layer model for the present
invention. The type and name of layers where operations are carried
out are only by way of example, and the present invention may be
applied to various systems where the N process SAW scheme based
HARQ method is used. In the layer 1/MAC layer, received packets
with CRC are subjected to error detection, and in response to error
detection (or detection of significant errors exceeding acceptable
level) as indicated in CRC-NG in the illustration, retransmission
of the error packet is requested. In the RLC/ARQ layer, it is
determined whether the sequence numbers SNs are consecutive, and if
it is detected that a certain sequence number is missing, it is
determined whether retransmission of the relevant packet must be
truly requested. Then, if so, the retransmission is requested.
While data transmission from the RLC/ARQ layer to an upper layer is
carried out in ISD, the order may not be conserved in data
transmission from the MAC layer to the RLC/ARQ layer. In other
words, the transmission is carried out in Out of Sequence Delivery
(OSD). Unlike conventional schemes, the order conservation is
conducted based on not the sequence number (TSN number) in the HARQ
layer but the sequence number (SN number) in the ARQ layer. For
this reason, there is a single transmission window in the
transmission stalling. Note that the sequence numbers in the HARQ
layer and the ARQ layer may be integrated and managed. In
application to the above-mentioned example, the packet order is
conserved by using the transmission window having the size of 2,048
sequence numbers, and the other transmission window having the size
of 16 TSN numbers is not used. As a result, it is possible to
substantially avoid degraded throughput as conventionally
experienced. However, the present invention differs from
conventional techniques in triggering of retransmission requests in
the RLC/ARQ layer. Even if it is detected that a certain sequence
number is missing, retransmission is not requested before it is
determined that retransmission of the relevant packet must be truly
requested. In this manner, triggering of the retransmission
requests is improved, resulting in omission of one of the two
transmission stalling operations, and thus well-ordered packets can
be promptly forwarded to an application layer and other layers.
First Embodiment
[0033] Hereinafter, one embodiment of the present invention will be
described in the context of downlink transmission from a base
station to a mobile station. However, the present invention can be
also applied to the inverse data transmission direction.
[0034] FIG. 6 shows a schematic block diagram illustrating a base
station and a mobile station operating in the HARQ method according
to one embodiment of the present invention, and FIG. 7 shows an
exemplary operation thereof. A retransmission request operation is
described in detail with reference to FIG. 8. IP packets A, B, C, .
. . from an upper apparatus are consecutively stored in an ARQ or
reception buffer (FIG. 6) in the base station (S1 in FIG. 7). The
received IP packets may be divided into fixed length blocks in the
ARQ buffer in FIG. 6. The present invention can be used regardless
of the PDU size. Thus, the PDU size is made uniform in the
illustration in FIG. 7, but various sizes of PDU may be used. For
convenience, transmitted packets are identified with the sequence
number (SN=1, 2, . . . ).
[0035] These packets are radio transmitted in physical channels and
are received at a mobile station (S2). The process number (P1, P2,
. . . ) is assigned to processes for transmitting information
specified with the SN. The mobile station conducts error detection
on the received packets, and if an error is detected as shown in
"NG", the mobile station requests the base station to retransmit
the relevant packets. For simplicity of explanation, the
retransmission request at this stage is referred to as "HARQ
retransmission request". Processing units as shown in "HARQ" in the
base station and the mobile station in FIG. 6 are responsible for
operations associated with the retransmission request in the layer
1/MAC layer.
[0036] The received packets are stored in the ARQ buffer (S3). The
ARQ is used to buffer the received packets like the RLC buffer in
FIG. 2, but the ARQ buffer may operate differently from the RLC
buffer in coordination with the retransmission control unit, for
example, in that it may refrain from the retransmission requests
even in cases of the packet order being inconsecutive in the
buffer. In these cases, it is determined whether the sequence
numbers SN for the packets stored in the ARQ buffer are
inconsecutive, and if needed, a retransmission request is issued.
For Simplicity of explanation, the transmission request in this
stage is referred to as "ARQ retransmission request".
[0037] The mobile station forwards error free packets to an upper
layer (an application layer and/or others) above the RLC. For a
packet including an error detected block, the mobile station waits
for an appropriate packet and forwards the retransmitted packet
after completion of the retransmission operation (S4).
[0038] FIG. 8 is a flowchart illustrating an exemplary operation
associated with a retransmission request. The operation illustrated
in this flowchart is mainly carried out in the retransmission
control unit in a mobile station. At step S1, the mobile station
receives and decodes a downlink shared control channel.
[0039] At step S2, it is determined whether there exists data
destined for the mobile station. If no data is destined for the
mobile station, the control proceeds to step S3 where the mobile
station waits for the next transmission time interval. Then, the
control returns to step S1.
[0040] At step S4, the mobile station receives and decodes the data
destined for itself in a shared data channel.
[0041] At step S5, the mobile station conducts error detection on
the decoded packets. If a significant error exceeding an acceptable
level is detected, the control proceeds to step S6 where the mobile
station request a base station to retransmit the relevant packet.
Then, the control returns to step S1.
[0042] At step S7, if no error or an error less significant than
the acceptable level is detected, the mobile station transmits
confirmation responses (ACK) for the packets. The confirmation
response indicates that the relevant packet has been properly
received in the mobile station.
[0043] At step S8, the sequence number of the properly received
packet is identified, and then it is determined whether the
identified sequence number is the smallest in packets to be
received. In other words, it is determined whether the order of the
packets to be acknowledged is consecutive. If the identified
sequence number is the smallest, the control proceeds to step S3
and then returns to step S1. For example, assuming that the packet
of the sequence number SN=1 has been just received, the next
smallest sequence number becomes 2. On the other hand, if the
identified sequence number does not correspond to the smallest
sequence number, the control proceeds to step S9. This may
correspond to a situation where after proper reception of the
packet of SN=1, the packet of SN=2 becomes a packet to be
retransmitted and the packet of SN=3 has been properly
received.
[0044] At step S9, it is determined whether there is an HARQ
process (retransmission process) where the retransmission operation
has not been finished. This determination is made, for example, by
the retransmission control unit verifying operations in the HARQ
processing unit. If there is no retransmission process that has not
been finished, the control proceeds to step S10. Otherwise, the
control proceeds to step S12.
[0045] At step S10, the mobile station requests the base station to
retransmit a missing packet identified at step S8 (ARQ
retransmission request). Subsequently, the control proceeds to step
S11 where the mobile station waits for the next transmission time
interval. Then, the control returns to step S1. According to the
embodiment of the present invention, unlike conventional schemes,
even if the order of packets to be acknowledged is not consecutive,
a retransmission request is not immediately issued. It is
determined at step S9 whether an unfinished retransmission process
exists, and if no unfinished retransmission process exists, the
retransmission request is issued. As a result, it is possible to
advantageously avoid unnecessary retransmission requests.
[0046] At step S12, the mobile station stores in a memory which
packet is being retransmitted (specifically, the sequence number of
the packet) and the process number of the process by which the
packet is to be retransmitted.
[0047] At step S13, after all stored processes where the packets
are under retransmission have been finished, the retransmitted
packets whose sequence numbers are stored at step S12 are subjected
to error detection.
[0048] At step S14, the retransmitted packets are subjected to
error detection. If an error is within the acceptable range, the
relevant packet is stored in the ARQ buffer. The control proceeds
to step S3 where the mobile station waits for the next transmission
time interval. Then, the control returns to step S1. On the other
hand, if the error exceeds the acceptable level, the control
proceeds to step S10 where the mobile station requests the base
station to retransmit the improperly received packet (ARQ
retransmission request). For example, this may correspond to
situations where the maximum time of retransmission has been
carried out but the packet could not be received with satisfactory
quality and/or where the packet has not been received with
satisfactory quality during a predefined period of delay time. The
control proceeds to step S11 where the mobile station waits for the
next transmission time interval. Then, the control returns to step
S1.
[0049] The specific embodiments of the present invention have been
described above, but the present invention is not limited to the
embodiments and various modifications and variations can be made
within the spirit of the present invention.
[0050] This international patent application is based on Japanese
Priority Application No. 2005-379990 filed on Dec. 28, 2005, the
entire contents of which are hereby incorporated by reference.
* * * * *
References