Lossless SRNS relocation procedure in a wireless...

Telecommunications – Radiotelephone system – Zoned or cellular telephone system

Reexamination Certificate

Rate now

  [ 0.00 ] – not rated yet Voters 0   Comments 0

Details

C455S438000, C455S440000, C455S442000, C370S331000

Reexamination Certificate

active

06725040

ABSTRACT:

BACKGROUND OF INVENTION
1. Field of the Invention
The present invention relates to a wireless communications network. In particular, the present invention discloses a method for performing lossless relocation of a serving radio network subsystem.
2. Description of the Prior Art
Please refer to FIG.
1
.
FIG. 1
is a block diagram of a wireless communications network
10
. The wireless communications network
10
comprises a plurality of radio network subsystems (RNSs)
20
in communications with a core network (CN)
30
. Each RNS
20
comprises one radio network controller (RNC)
22
that is in communications with a plurality of node Bs
24
. Each node B
24
is a transceiver, which is adapted to send and receive wireless signals. In particular, the wireless communications network
10
assigns a mobile unit
40
to a particular RNS
20
, which is then termed the serving RNS (SRNS)
20
s
of the mobile unit
40
. Data destined for the mobile unit
40
is sent by the CN
30
to the SRNS
20
s
. This data is in the form of service data units (SDUs)
28
that are held by the RNC
22
of the SRNS
20
s
pending transmittal by one of the Node Bs
24
. The RNC
22
selects a node B
24
that is best able to accurately transmit the SDUs
28
to the mobile unit
40
. Such a selection will depend, for example, upon the location of the mobile unit
40
within the domain of the SRNS
20
s
. The mobile unit
40
broadcasts SDUs
48
to the wireless communications network
10
, which are then picked up by the SRNS
20
s
and forwarded to the CN
30
. Occasionally, the mobile unit
40
may move close to the domain of another RNS
20
, which is termed a drift RNS (DRNS)
20
d
. A node B
24
of the DRNS
20
d
may pick up one or more of the SDUs
48
transmitted by the mobile unit
40
. The RNC
22
of the DRNS
20
d
forwards the received SDUs
48
to the SRNS
20
s
. The SRNS
20
s
then forwards these received SDUs
48
to the CN
30
. Consequently, all communications between the mobile unit
40
and the CN
30
must pass through the SRNS
20
s.
Please refer to
FIG. 2
in conjunction with FIG.
1
.
FIG. 2
is a block diagram of the RNC
22
of the SRNS
20
s
. Communications between the mobile unit
40
and the RNC
22
are effected through a multi-layered communications protocol that has a packet data convergence protocol (PDCP) layer
22
p
in communications with an upper layer
22
u
and a lower layer
22
L. The PDCP layer
22
p
receives a plurality of SDUs
28
from the upper layer
22
u
. Each SDU
28
includes a header
28
h
and data
28
d
. The primary purpose of the SDU
28
is to carry the data
28
d
to a destination indicated by the header
28
h
. The header
28
h
is analogous to an Internet protocol (IP) header. The header
28
h
may carry a lot of information that is redundant or repeated through the other SDU headers
28
h
in the other SDUs
28
. One purpose of the PDCP layer
22
p
is to compresses the headers
28
h
so as to maximize bandwidth. This compression is performed by way of a header compressor/decompressor
22
c
. The header compressor/decompressor accepts an SDU
28
and generates a PDCP protocol data unit (PDCP PDU)
29
. A PDCP PDU
29
includes a PDCP header
29
h
and data
29
d
. The data
29
d
includes compressed header data
29
x
that is generated by the header compressor/decompressor
22
c
according to the header
28
h
. Each PDCP PDU
29
s
is incrementally assigned a 16-bit sequence number (SN)
29
s
by the PDCP layer
22
p
. That is, each sequentially successive PDCP PDU
29
is assigned an incrementally higher SN
29
s
. For example, a first PDCP PDU
29
may be assigned an SN
29
s
of 62. A second PDCP PDU
29
immediately after the first PDCP PDU
29
would thus be assigned an SN
29
s
of 63, and so on. The SNs
29
s
are not actually a part of the PDCP PDUs
29
, but are internally maintained by the PDCP layer
22
p
. The PDCP PDUs
29
are then delivered to the lower layer
22
L for transmission. As there is a one-to-one correspondence between PDCP PDUs
29
and SDUs
28
, and as each PDCP PDU
29
has an assigned SN
29
s
, each corresponding SDU
28
also has an associated SN
29
s
. That is, the SNs
29
s
are associated with both the PDCP PDUs
29
and the corresponding SDUs
28
. Since bandwidth is to be maximized by the compression of the headers
28
h
, each PDCP PDU
29
should, ideally, be smaller in size than its corresponding SDU
28
. To ensure that this is indeed the case, the PDCP header
29
h
should be kept as small as possible. The type of header compression used for the header compressor/decompressor
22
c
will depend upon the format of the headers
28
h
. As an example, though, if the headers
28
h
are IP headers, then the compression performed could conform to the IP industry standard RFC 2507.
Similarly, PDCP PDUs
27
received from the lower layer
22
L (i.e., originating from the mobile unit
40
) are fed into the header compressor/decompressor
22
c
to generate the corresponding SDUs
48
. The SDUs
48
so generated are then delivered to the upper layer
22
u
. Each PDCP PDU
27
has a 16-bit SN
27
s
assigned to the PDCP PDU
27
by the PDCP layer
22
p
, in a manner that is analogous to the SNs
29
s
. These SNs
27
s
are also associated with the corresponding SDUs
48
.
As the mobile unit
40
moves closer towards the domain of the DRNS
20
d
, more and more SDUs
48
are received and forwarded by the DRNS
20
d
. Eventually, a decision is made by the wireless network
10
to place the mobile unit
40
under the DRNS
20
d
, and a transfer process is enacted. This process is termed a SRNS relocation procedure, and should be lossless. Lossless means that no SDUs
28
,
48
are lost during the relocation procedure. Please refer to
FIG. 3
in conjunction with
FIGS. 1 and 2
.
FIG. 3
is a block diagram of the mobile unit
40
undergoing a lossless SRNS relocation procedure. The DRNS
20
d
becomes a target RNS (TRNS)
20
t
. After completion of the relocation procedure, the TRNS
20
t
will serve as the new SRNS
20
s
for the mobile unit
40
. In order for the TRNS
20
t
to properly take up its job as the new SRNS
20
s
for the mobile unit
40
, the current SRNS
20
s
must forward key information to the TRNS
20
t
. Please refer to
FIG. 4
in conjunction with
FIGS. 2 and 3
.
FIG. 4
is a message sequence chart for the prior art lossless SRNS relocation procedure. The SRNS
20
s
sends forwarding information
50
to the TRNS
20
t
. This forwarding information includes a downlink sending sequence number (DL Send_SN)
52
, an uplink receiving sequence number (UL Receive_SN)
54
, and all unconfirmed SDUs
28
. The multi-layered communications protocol used by both the SRNS
20
s
and the mobile unit
40
enables the mobile unit
40
to confirm those PDCP PDUs
29
transmitted by the SRNS
20
s
that are successfully received by the mobile unit
40
. Any PDCP PDUs
29
not explicitly confirmed as received by the mobile unit
40
are termed unconfirmed PDCP PDUs
29
. As there is a one-to-one correspondence between SDUs
28
and PDCP PDUs
29
, an unconfirmed PDCP PDU
29
means that there is a corresponding unconfirmed SDU
28
. These unconfirmed SDUs
28
are forwarded by the SRNS
20
s
to the TRNS
20
t
. The DL Send_SN
52
is the value of the SN
29
s
associated with the sequentially earliest unconfirmed PDCP PDU
29
. As the SNs
29
s
are not explicitly carried in the SDUs
28
, this enables the TRNS
20
t
to properly associate an SN
29
s
for the corresponding PDCP PDU
29
of each forwarded SDU
28
. The UL Receive_SN
54
is the value of the SN
27
s
associated with the PDCP PDU
27
that the SRNS
20
s
next expects to receive from the mobile unit
40
. This enables the TRNS
20
t
to properly associate an SN
27
s
for each subsequently received PDCP PDU
27
from the mobile unit
40
. The TRNS
20
t
sends the UL Receive SN
54
to the mobile unit
40
. From this, the mobile unit
40
can determine which packets
48
to begin sending to the TRNS
20
s
under its guise as the new SR

LandOfFree

Say what you really think

Search LandOfFree.com for the USA inventors and patents. Rate them and share your experience with other people.

Rating

Lossless SRNS relocation procedure in a wireless... does not yet have a rating. At this time, there are no reviews or comments for this patent.

If you have personal experience with Lossless SRNS relocation procedure in a wireless..., we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Lossless SRNS relocation procedure in a wireless... will most certainly appreciate the feedback.

Rate now

     

Profile ID: LFUS-PAI-O-3242979

  Search
All data on this website is collected from public sources. Our data reflects the most accurate information available at the time of publication.