Telecommunications – Transmitter and receiver at same station – Radiotelephone equipment detail
Reexamination Certificate
1998-03-03
2001-02-27
Nguyen, Lee (Department: 2683)
Telecommunications
Transmitter and receiver at same station
Radiotelephone equipment detail
C455S039000, C455S177100, C455S266000, C370S342000
Reexamination Certificate
active
06195565
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to the control of bandwidth in a packet-based data system.
2. Description of the Related Art
FIG. 1
shows a schematic block diagram of a conventional multipoint-to-point packet-based data system
100
, such as those used for computer networks and telecommunications systems, in which a base station
102
communicates with a number of network nodes referred to here as network interface units (NIUs)
104
. In the downstream direction, transmitter
106
of base station
102
transmits packets of data to the NIUs
104
. In the upstream direction, one or more of the NIUs
104
transmit packets of data to receiver
108
of base station
102
. In one possible implementation, the data packets are interleaved in the upstream and downstream directions using a time division multiple access (TDMA) scheme. The base station and the NIUs are the various nodes in the data system, with the base station controlling the bandwidth in the network (e.g., the allocation to the various NIUs of time slots for upstream transmissions).
When used, for example, in a telecommunications application, each NIU
104
in data system
100
provides the interface to the data system for a telephone or other node in the network, and base station
102
may be a switch in a central office or other component that communicates with multiple NIUs. In such an application, each NIU
104
is capable of sending control messages to base station
102
. Control messages are information exchanged between NIUs and the base station that allow the base station to properly monitor and maintain communication channels within the allocated bandwidth of the communication system. The control messages may be embedded, for example, in the packets sent from the NIU to the base station in the upstream direction using the well-known slotted ALOHA technique. When a phone call is to be terminated at a particular NIU
104
, the base station
102
assigns a particular channel for that NIU to use for its upstream communications. However, when a particular NIU wants to initiate a phone call, it must send an upstream control message to the base station requesting bandwidth for the phone call. Since the NIU does not have a particular channel already assigned, it may arbitrarily or randomly select a channel for its bandwidth request message. This upstream message may collide with one or more other upstream messages being sent to the base station from one or more other NIUs in the same channel, leading to corrupted messages which the base station cannot accurately process.
According to the slotted ALOHA technique, a collision/back-off algorithm is followed when two or more NIUs attempt to send such control messages at the same time to ensure successful NIU-to-base-unit message communications. One conventional collision/back-off algorithm calls for each competing NIU to retransmit its bandwidth request after delaying for a random period of time. Unfortunately, when many NIUs attempt to send control messages at the same time, the resulting collisions, retries, and further collisions may effectively block almost all upstream message transmission. This is undesirable, since such an overload condition could in theory happen during exceptionally high call volumes, which would limit the ability of the system to allocate bandwidth to the NIUs (e.g., providing dial tone to new calls for telephony systems).
SUMMARY OF THE INVENTION
The present invention is directed to a back-off strategy that addresses the problems that can arise from message collisions in heavily populated packet-based data systems.
According to one embodiment, the present invention is a method of controlling bandwidth in a packet-based data system comprising a base station and a plurality of network interface units (NIUs). The base station transmits special data to the NIUs, wherein the NIUs are organized into two or more groups and the special data identify which groups of NIUs are authorized to transmit upstream messages to the base station. Only authorized NIUs transmit upstream messages to the base station.
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Dempsey Peter A.
Lee Kyoo J.
Warmink Stuart
Lucent Technologies - Inc.
Mendelsohn Steve
Nguyen Lee
Nguyen Simon
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