Multiplex communications – Communication over free space – Having a plurality of contiguous regions served by...
Reexamination Certificate
1999-09-14
2003-10-07
Trost, William (Department: 2683)
Multiplex communications
Communication over free space
Having a plurality of contiguous regions served by...
C370S342000, C455S522000
Reexamination Certificate
active
06631123
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention is generally related to a method of improving a user's ability to gain access to a communication system and in particular to a method of adjusting the power of a user equipment probing signal to increase the likelihood of detection by the communication system equipment.
2. Description of the Related Art
Communication systems, and in particular, wireless communication systems comprise a plurality of communication channels through which subscribers of such systems communicate with each other and with the system. A portion of a typical wireless communication system is shown in FIG.
1
. The wireless communication system of
FIG. 1
depicts a cellular system comprising cells (e.g.,
102
,
104
,
106
,
108
) whereby each cell is a symbolic representation of the physical terrain or geographical region covered by communication network equipment commonly known as cell sites or base stations (e.g.,
110
,
112
,
114
). Each base station has system equipment comprising radio equipment (i.e., transmitter, receiver, modulator, demodulator) that are used to transmit and/or receive communication signals between a base station and a user equipment. The system equipment can also be located at places other than base stations. The term “user” hereinafter is used interchangeably with the term “subscriber” to indicate an entity (i.e., person, facility or a combination thereof) who is allowed access (when possible) to the communication system. Access to the communication system is the ability of a subscriber to make use of the resources (e.g., system equipment, communication channels) of the communication system. The user equipment (e.g.,
140
in cell
104
) is typically a cellular phone or any other communication equipment that is used by a subscriber of a communication system. For example, the user equipment can be a wireless portable computer or a pager. The system equipment further comprises processing equipment for retrieving information being carried by the communication signals and for implementing procedures based on communication protocols. A communication protocol is a set of procedures or processes that dictate how communications between users of the communication system is to be initiated, maintained and terminated. The communication protocol also dictates the communications between a user and system equipment. Communication protocols are part of well known and established standards that are followed by operators of communication systems.
Still referring to
FIG. 1
, each user communicates with a base station via a wireless communication link. For example in cell
104
, user
140
communicates with base station
114
via communication link
156
. Typically, each wireless communication link comprises several communication channels. For example, for a Code Division Multiple Access (CDMA) wireless system, the communication link comprises an Access channel, a Paging channel and a Traffic channel. The Access channel is a channel through which user equipment transmits protocol information to a base station. The protocol information is information used by the system equipment operate and/or control the communication system. For example, a user requesting access to the communication system is allowed to use the communication system after various protocol information have been exchanged between the base station and the user equipment. In allowing the user to have access to the communication system, the system equipment identifies the user as a subscriber of the system, finds resources (e.g., communication channels, base station equipment) that can be made available to the user and allows the user to use (transmit/receive information) such resources in accordance with the protocol being followed by the communication system. The Paging channel is a channel through which system equipment (e.g., base station) broadcasts protocol information to users of the communication system. The traffic channel is the channel used by the users to communicate with each other or with the system. The information conveyed through the traffic channel is, for example, voice, data, video, facsimile information or any other information typically conveyed by users of communication systems. The traffic channel consists of two channels: the first channel is called the reverse link through which users transmit information which information is received by the base station (or other system equipment); the second channel is called the forward link through which the base station (or other system equipment) transmits information to a user. Each user has a forward link and a reverse link assigned by the communication system. In addition to the other channels discussed above, some CDMA systems also have a pilot channel that is used to assist a user to obtain access to the communication system.
The pilot channel is a channel through which the system equipment broadcasts, on a continuous basis, a pilot signal that covers a certain area (e.g., cell area) of the communication system. The pilot signal serves as a sort of beacon signal that assists users to obtain access to the communication system. The pilot signal is also one of several signals used by users to synchronize their timing to the timing of the communication system.
A user initiates a request for access to the communication system by transmitting a protocol signal called a probe signal. The probe signal has two portions: the first portion is called the preamble which is typically a repetitive signal (i.e., a string of “0” bits or a string of “1” bits); the second portion is a message portion containing protocol information. The preamble is the portion of the probe that allows the base station (or other system equipment) to detect the probe. The probe signal once detected by the system equipment initiates a certain procedure (in accordance with a protocol being followed by the communication system) to provide access to the user that transmitted the probe signal. Prior to initiating the procedure, the system equipment transmits an “acknowledge” (ACK) message to the user equipment indicating to the user equipment that the probe signal has been detected. Once the user equipment receives the ACK message it no longer transmits the probe signal and proceeds as per the protocol to obtain access to the communication system.
In many cases the probe signal is not detected by the system equipment. In such cases, the user equipment transmits the probe signal repeatedly until it receives the ACK message. For each repeated transmission of the probe signal, the power of the probe signal is increased by a system defined amount hereinafter referred to as “&Dgr;.” A graph of the power of the probe signal versus time is shown in FIG.
2
. Each probe is transmitted after a certain time interval &tgr;+&tgr;
r
i
where &tgr; is a system defined time interval and &tgr;
r
i
is a time interval of random length for the i
th
probe signal. Thus, according to the graph of
FIG. 2
, the first probe has a power of P
1
, the second probe has a power of P
2
, the third probe has a power of P
3
and so on. In general, the probe power can be expressed by the following equation:
(
1
) P
i
=P
0
+&Dgr;i where the i
th
probe has power P
i
and the initial probe power is P
0
. P
0
is a system defined value that represents the initial probe power after having been modified based on the measured power of the pilot signal.
The base stations are designed to simultaneously receive signals from a plurality of users. For example, base station
114
in cell
104
not only receives the probe signal from user
136
, but also receives other signals from the other users (e.g., user
146
, user
144
, user
140
, user
138
) in cell
104
. From the point of view of user
136
, the signals from the other users adversely affect base station
114
's ability to detect a probe signal from user
136
. The signals from other users—from the point of view of user
136
—are interference that interfere with the detection of a
Jiang Frances
Qiu Robert Caiming
Wang Liwa
Zhu Pengfei
Lucent Technologies - Inc.
Torres Marcos L
Trost William
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