Sub-channels for the random access channel in time division...

Details Sub-channels for the random access channel in time division... Sub-channels for the random access channel in time division...

2001-12-12

2004-08-03

Olms, Douglas (Department: 2661)

Multiplex communications

Communication over free space

Combining or distributing information via code word channels...

C370S342000, C370S441000

Reexamination Certificate

active

06771632

ABSTRACT:

BACKGROUND
The invention generally relates to wireless time division duplex (TDD) communication systems using code division multiple access. In particular, the invention relates to sub-channels for the physical random access channel (PRACH) for such systems.
In code division multiple access (CDMA) communication systems using frequency division duplex (FDD), such as proposed for the third generation partnership project (3GPP), physical random access channels (PRACHs) are used for transmitting infrequent data packets and system control information from the user equipments (UEs) or users to the Node-B.
In a 3GPP FDD/CDMA system, the PRACH is divided into ten (10) millisecond radio frames
22
1
to
22
8
(
22
) having fifteen (15) timeslots
24
, as shown in FIG.
1
. The radio frames
22
are sequentially numbered, such as numbered from 0 to 255, as a system frame number. The system frame numbers are sequentially repeated. The random access transmission starts at the beginning of a number of well-defined time intervals, denoted access slots
26
. The random access transmissions
28
1
to
28
5
(
28
) from the users are begun in a particular access slot
26
and continue for one or multiple slots
26
. These transmissions are sent using a randomly selected signature associated with an access service class (ASC) assigned by a radio resource controller of the network to the user.
The PRACH is used for infrequent data packets and system control information and the network uses sub-channels of the PRACH for further separation of UEs and access service classes. In the 3GPP FDD/CDMA system, each sub-channel is associated with a subset of the total uplink access slots
26
, described as follows.
Two sequential radio frames
22
are combined into one access frame
20
. The access frame is divided into 15 access slots
26
. Each access slot
26
has a duration of two radio frame timeslots
24
as shown in FIG.
1
. The duration of a radio frame
22
is shown in
FIG. 1
by the dual headed arrows. The sub-channels are assigned to the access slots
26
by sequentially numbering the slots from 0 to 11, as shown in FIG.
1
. After sub-channel
11
is assigned, the next access slot
26
is numbered 0 and the numbering is repeated. The access slot
26
to sub-channel numbering is repeated every 8 radio frames or 80 milliseconds (ms). This repetition can be viewed as a modulo (mod)
8
counting of the radio frame numbers.
In 3GPP FDD/CDMA, multiple PRACHs are used. Each PRACH is uniquely associated with a random access channel (RACH) transport channel and is also associated with a unique combination of preamble scrambling code, available preamble signatures and available sub-channels.
FIG. 2
is one example of an illustration of such an association. RACH
0
30
0
is paired with PRACH
0
32
0
through a coding block
31
0
. The data received over PRACH
0
32
0
is recovered using the preamble scrambling code
0
34
0
and the appropriate preamble signature
38
that the data was sent.
PRACH
0
32
0
is uniquely associated with preamble scrambling code
0
34
0
and has three access service classes (ASCs), ASC
0
40
0
, ASC
1
40
1
and ASC
2
40
2
. Although the number of ASCs shown in this example are three, the maximum number of ASCs is eight (8). Each ASC
40
has a number of available sub-channels, available preamble signatures and a persistence factor. The persistence factor represents the persistence in retransmitting the preamble signature after a failed access attempt. In 3GPP FDD/CDMA, the maximum available sub-channels
36
is 12 and the maximum available preamble signatures
38
is 16.
RACH
1
30
1
is paired with PRACH
1
32
1
. PRACH
1
32
1
is uniquely associated with preamble scrambling code
1
34
1
and its sub-channels
36
and preamble signatures
38
are partitioned into four ASCs
40
, ASC
0
40
3
, ASC
1
40
4
, ASC
2
40
5
and ASC
3
40
6
. RACH
2
30
2
is paired with PRACH
2
32
2
. PRACH
2
32
2
uses preamble scrambling code
2
34
2
, which is also used by PRACH
3
32
3
. Three ASCs
40
are available for PRACH
2
32
2
, ASC
0
40
7
, ASC
1
40
8
and ASC
2
40
9
. Because PRACH
2
and PRACH
3
share the preamble scrambling code, a group of partitioned off available sub-channels/available preamble signature combinations are not used for PRACH
2
32
2
. The partitioned off area is used by PRACH
3
32
3
.
RACH
3
30
3
is paired with PRACH
3
32
3
. PRACH
3
32
3
also uses preamble scrambling code
2
34
2
and uses ASC
0
40
10
and ASC
1
40
11
. ASC
0
40
10
and ASC
1
40
11
contain the available sub-channel/signature set not used by PRACH
2
32
3
.
Since each PRACH ASC
40
is uniquely associated with a preamble scrambling code
34
and available preamble signatures set and sub-channels, the Node-B can determine which PRACH
32
and ASC
40
is associated with received PRACH data. As a result, the received PRACH data is sent to the appropriate RACH transport channel. Although each PRACH
32
is illustrated in this example by having the ASCs
40
partitioned by available preamble signatures, the partitions may also be by sub-channel
36
.
Another communication system proposed to use PRACHs is a CDMA system using time division duplex (TDD), such as the proposed 3GPP TDD/CDMA system. In TDD, radio frames are divided into timeslots used for transferring user data. Each timeslot is used to transfer only uplink or downlink data. By contrast, an FDD/CDMA system divides the uplink and downlink by frequency spectrum. Although the air interface, physical layer, between FDD and TDD systems are quite different, it is desirable to have similarities between the two systems to reduce the complexity at the network layers, such as layer
2
and
3
.
Accordingly, it is desirable to have sub-channels for the RACH for TDD.
SUMMARY
Sub-channels are defined for a physical random access channel of a wireless time division duplex communication system using code division multiple access. A series of radio frames have a sequence of timeslots. For a particular timeslot number of the sequence, each sub-channel of the particular timeslot number is uniquely defined by one radio frame of the series.


REFERENCES:
patent: 5822359 (1998-10-01), Bruckert et al.
patent: 6031832 (2000-02-01), Turina
patent: 6400695 (2002-06-01), Chuah et al.
patent: 6584087 (2003-06-01), Czaja et al.
patent: 6594240 (2003-07-01), Chuah et al.
patent: 0994634 (1999-10-01), None
Authored by ETSI, Universal Mobile Telecommunications System (UMTS); Physical layer procedures (FDD) (#GPP TS 25.214 version 3.4.0 Release 1999), published by ETSI, pp. 1-47 .*
Chuah et al., “Access Priority Schemes in UMTS MAC” Sep. 1999 IEEE, pp. 781-786.
“Universal Mobile Telecommunciatons System (UMTS); Physical Lay Procedures (FDD)” Sep. 2000, 3GPP, pp. 1-47.

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