Multiplex communications – Communication over free space – Having a plurality of contiguous regions served by...
Reexamination Certificate
1999-02-26
2004-05-25
Pham, Chi (Department: 2662)
Multiplex communications
Communication over free space
Having a plurality of contiguous regions served by...
C370S392000, C370S401000, C370S475000
Reexamination Certificate
active
06741575
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to systems and methods of providing mobile cellular communications, and in particular, to a method and system for Internet services in a mobile cellular communications network.
2. Description of the Related Art
Traditionally, cellular mobile and wireless communication systems have been designed and built for voice service. With the explosive growth of Internet applications and users, there is an increasing demand on providing Internet service to mobile users based on the existing cellular systems. Voice communication is characterized as connection-oriented, circuit-switching, constant bit-rate, and low tolerance to loss and jitter. In contrast, Internet service is characterized by connectionless communication, packet-switching, bursty traffic patterns, multicast, differentiation of multiple classes of services, and often, best effort and loss-tolerant communication. In addition, some Internet applications desire much higher and often on-demand bandwidth such as videoconferencing using variable-bit-rate coding. Thus far, the development of a cost effective network architecture and necessary system components to meet these different requirements of Internet service on top of the existing infrastructure of voice-oriented cellular networks has remained an elusive goal.
FIG. 1
is a depiction of a PACS (Personal Access Communication System)
100
. The PACS is an emerging low-tier, low-cost PCS standard for cellular wireless services in densely populated areas. The PACS standard defines two data communication modes (circuit-mode and packet-mode).
In a PACS network
100
, users obtain services through subscriber unit (SU) devices
102
. SUs
102
communicate with radio ports (RPs) through a time division multiple access (TDMA) uplink and time division multiplexing (TDM) downlink. The influence of the RPs
104
, as determined by their transmission and reception range and that of the SUs
102
, define cells
112
.
Nearby RPs
104
are controlled by a radio port control unit (RPCU)
106
, which concentrates all traffic from the RPs
104
and connects it to a backbone voice or data network. User authorization and other related functions are provided by an access manager (AM)
108
and a signaling network
110
.
The PACS standard packet-mode data service serves as the fundamental building block for implementing and managing IP services in the Internet service architecture of the present invention.
The packet-mode data service of PACS, known as PACS Packet Channel (PPC), provides the user with a variable bandwidth, asynchronous, bandwidth-on-demand, and asymmetric data service at data rates up to 256 thousand bytes per second (Kbps). It is based on frequency-division-duplex, TDMA uplink and TDM downlink PACS physical interface which is common to both circuit-mode and packet-mode services. Uplink refers to the direction from SU
102
to RPCU
106
, and downlink is from RPCU
106
to SU
102
.
The high data rate and variable bandwidth nature of PPC is well suited to multimedia and the bursty nature of Internet traffic. PPC supports dynamic sharing of bandwidth with the PACS circuit mode services (voice, circuit-mode data, etc.), allowing PPC to utilize the bandwidth otherwise idle.
FIG. 2A
is a diagram presenting a depiction of PPC layers. The PPC consists of three layers: a PACS physical layer
202
, datalink layer (DL)
204
and security layer (SL)
206
. The PACS physical layer performs coding of TDMA uplink and TDM downlink. Both uplink TDMA and downlink TDM frames are 2.5 msec long. Each frame consists of 8 slots and each slot is 10 bytes long. The task of the PPC DL layer
204
is to provide a reliable and connectionless communication service to the SL layer
206
, which includes medium access control (MAC), fragmentation and segmentation, and error detection and correction. The major functions of SL layer
206
include handset registration, user authentication, and data encryption.
FIG. 2B
illustrates the PACS standard encapsulation and framing procedure. First, the PPC copies each network layer packet
210
in an SL packet
212
with a header
214
and checksum
216
with optional payload encryption to prevent eavesdropping over the air. It then encapsulates each SL packet
212
in a DL packet
218
with proper header
220
and checksum
222
. Each DL packet
218
is divided into one or more DL fragments
224
and finally each DL fragment
224
is subdivided into DL segments
226
. Fragmentation is for the high-level medium access function—the PPC must assign a slot number (out from the 8 slots) for each DL fragment
224
, and all segments of a fragment
224
must be transmitted in the same slot. Segmentation is to fit the TDM/TDMA airlink structure, which is depicted in FIG.
2
C.
For downlink fragmentation, the maximum fragment size is 576 bytes of data. A larger packet must be fragmented but each fragment can be transmitted in different slots in parallel. Uplink fragments may be 256 segments long, therefore all uplink DL packets
218
are sent in a single fragment.
FIG.
2
D and
FIG. 2E
are diagrams depicting the encapsulation uplink and downlink messages in greater detail.
FIG. 3
is a diagram of the functional architecture of the PPC. A contention function (CF)
302
performs the small subset of DL medium access and acknowledgment procedures that are highly time critical. A packet data controller unit (PDCU)
304
handles the rest of the DL and SL functions. The CF
302
resides in the RP
104
, and PDCU
304
is typically implemented in the RPCU
304
.
Each packet-mode SU
102
has a subscriber identity (SubID). The SubID is only used to authenticate a user during registration. In addition, each active SU
102
also has a transient identifier called LPTID (Local Packet Terminal Identifier). The LPTID is a one-byte integer specifying the source/destination SU
102
in every uplink/downlink slot over the wireless link. Each time an SU
102
enters a cell
112
(by cold-start or roaming), it is assigned a unique LPTID for as long as it remains in the cell
112
. An LPTID is only valid in the current cell
112
and an SU
102
can have a different LPTID value in a different cell
112
. LPTIDs are assigned by the PACS network
100
after successful registration and re-assigned after each hand-off. When the SU
102
moves to an adjacent cell, the old LPTID will not be used any more, and a new LPTID must be allocated in the new cell
112
. The LPTID is thus transient in nature. Table I below shows the current allocation scheme for LPTID as defined in the standard.
TABLE 1
LPTID Value
Purpose
0 × 00
Null
0 × 01
Registration message (used before the SU 102 is
assigned an LPTID).
0 × 02 - 0 × EF
Assigned to SUs 102 upon registration and handoff.
This allows up to 238 SUs 102 in each cell 112.
0 × F0 - 0 × FD
Reserved for future use
0 × FE
System information (used to broadcast datalink layer,
network layer, and “system information channel”
parameters).
0 × FF
All SUs 102. (Used for messages that must be
broadcast to all SUs 102.)
After successful registration, each active SU
102
is assigned a datalink layer address for use in the current cell
112
. The datalink layer address is a one-byte integer called LPTID (Local Packet Terminal ID).
Whenever a SU
102
enters the network, it performs a PPC registration. Two major tasks of PPC registration are authentication and LPTID assignment. At the beginning of the registration, the SU
102
sends a registration request message (PACKET_REG_REQ) which includes its SubID (assuming no user anonymity). The AM
108
then authenticates the SU
102
using this SubID. Once the authentication is successful, the PDCU
304
assigns a new LPTID and sends the registration acknowledgment message (PACKET_REG_ACK) with this LPTID back to the SU
102
. From then on, the SU
102
identifies data destined for it by the LPTID until it de-registers from the network or-moves-to a different cell
112
.
A cell hand-off is known as an
Dao Son K.
Kailas Sivakamar
Kay Stanley E.
Khan Tayyab
Ryu Bo
Duraiswamy V. D.
Hughes Electronics Corporation
Pham Chi
Qureshi Afsar M
Sales M. W.
LandOfFree
Apparatus and method for efficient delivery of multicast... does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Apparatus and method for efficient delivery of multicast..., we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Apparatus and method for efficient delivery of multicast... will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-3186116