Telecommunications – Transmitter and receiver at same station – Radiotelephone equipment detail
Reexamination Certificate
2000-05-17
2001-08-21
Maung, Nay (Department: 2681)
Telecommunications
Transmitter and receiver at same station
Radiotelephone equipment detail
C455S039000, C455S444000, C455S448000, C455S466000, C455S525000, C370S477000
Reexamination Certificate
active
06278883
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The invention generally relates to wireless data communication; and in particular, the present invention relates to network access protocols used in wireless data communication.
2. Background of the Invention
Network access protocols exist for use in conjunction with a two-way wireless data network such as that shown in FIG.
1
and described in 759340
vl
detail in and commonly assigned U.S. patent application Ser. No. 08/542,860, entitled “TWO-WAY WIRELESS DATA NETWORK”, of Weijia Wang, now U.S. Pat. No. 5,898,904, issued on Apr. 27, 1999, which is incorporated herein by reference in its entirety.
As shown in
FIG. 1
, a wireless data network
100
includes a wireless data terminal
101
, a cellularized base station
102
, message control center
103
, interfaces
105
-
109
to information and communication applications, and radio links
115
and
117
. Message control center
103
has a high power transmitter capable of broadcasting through the paging channel to wireless data terminals within the entire service area of wireless data network
100
. In this manner, wireless data network
100
is compatible with existing one-way paging services. Message control center
103
also communicates with base station
102
through radio link
117
which is a high power (e.g. 3 watts) transmission.
Base station
102
is one of a number of base stations that are distributed throughout the service area of wireless data network
100
, each base station serving a relatively small portion of the service area of wireless data network
100
within its immediate vicinity. The local service area of a base station is sometimes called a cell. The base stations broadcast to wireless data terminals in their respective cells through a local channel. It is desired that the base stations cumulatively serve all locations within the service area of the wireless data network
100
. Wireless data terminal
101
communicates with one or more of the base stations, for example base station
102
, through link
115
. Link
115
needs only provide a low power transmission (e.g. 100 mW) to cover a local area. At a location outside of the local service area of any base station, wireless data terminal
101
is restricted only to receiving messages from the 1-way paging channel. Other details of the operation of the two-way wireless data network can be found in the aforementioned copending patent application entitled “TWO-WAY WIRELESS DATA NETWORK” of Weijia Wang.
Base station
102
in wireless data network
100
uses a channel access protocol which allows all base stations within wireless network
100
to communicate with wireless data terminals over the same packet radio link at the same carrier frequency. An example of such an access protocol is disclosed in and commonly assigned U.S. patent application Ser. No. 08/542,770, entitled “WIRELESS NETWORK ACCESS SCHEME”, of Weijia Wang et al., now U.S. Pat. No. 5,721,733, issued on Feb. 24, 1998, which is incorporated herein by reference in its entirety.
The network access protocol described in Weijia Wang et al. provides for high channel utilization rate under both the ALOHA protocol and the carrier sensing multi-access (CSMA) protocol by making use of the FM capture effect. However, the network access scheme in Weijia Wang et al. can be enhanced to increase the bandwidth and channel utilization of the two-way wireless data network described above without costly replacement of existing transceivers.
In these wireless networks, to initiate communication with a wireless data terminal, a wake-up signal is first sent from a message control center (e.g. message control center
103
) to the wireless data terminal, before two-way communication is established between a local base station and the wireless data terminal. Because the high power transmitter of the message control center is a shared resource, under high message traffic conditions, an undesirable latency may be incurred. It would be desirable that, under certain conditions, the message control center can be bypassed in initiating local two-way communication, without at the same time surrendering the benefits described above.
Also, in wireless communication, to achieve a higher data rate, a transmitter is typically required to output a higher power. However, to achieve the mobility advantage of a wireless terminal, a wireless data terminal is typically powered by a battery, which must be provided with a reasonable service life-time between recharging operations. Thus, an increased data rate without a corresponding increase in the power requirement of the wireless data terminal is desired.
Other mechanisms for extending the wireless data terminal's limited service life-time between recharging are also desired.
SUMMARY OF THE INVENTION
According to the present invention, a network access protocol for a wireless data network is provided to increase the network bandwidth, improve transmission performance, and enhance mobility management.
In one embodiment, a two-way wireless data network of the present invention includes (a) wireless data terminals each capable of transmitting a radio signal of a local frequency over a predetermined range; and (b) one or more base stations having a radio signal transceiver, the base station serving a service area and capable of transmitting a radio signal of a second local frequency. The present invention provides a registration procedure whereby a wireless terminal can communicate, subsequent to the registration, with the base station within the predetermined range exclusively over the local frequencies. In that embodiment, each base station is required to transmit a data packet within a predetermined time interval. To achieve this goal, the base station can transmit a dummy data packet (“beacon”). A wireless data terminal checks periodically for such a data packet or beacon to determine if it is within the range of the base station. Upon detecting the beacon or the data packet, the wireless data terminal registers with the base station. To avoid an excessive number of registrations when a wireless terminal travels over the local service areas of a number of base stations, a “hysteresis” period is required after the wireless data terminal leaves the local service area of the base station it is registered with. During the hysteresis period, the wireless data terminal cannot register with another base station.
In one embodiment, the wireless data network includes a message control center broadcasting over a paging channel with a range covering the local service areas of the base stations within the wireless data network, thus providing in the paging channel a one-way messaging service to the wireless data terminals.
In one embodiment, the transmission rate used by the wireless data terminals is less than the transmission rate used by the base stations. In this wireless data network, an acknowledgment packet sent in respond to a data packet is transmitted at a different data rate from the data rate at which the data packet is sent. Thus, the network access protocol of the present invention conserves power for the wireless data terminals through the use of a dynamic data transmission rate.
According to another embodiment of the present invention, the base stations transmit at a higher power than the wireless data terminals, so that within the local service area of each base station there exist, with respect to the local channel, a two-way communication service area and a one-way communication service area outside of the two-way communication service area.
According to another aspect of the present invention, a data packet includes a first header and a second header. The first header includes a portion (e.g. 2 bits) of the full identification of the recipient, which is provided in the second header. Each wireless data terminal parses the first header to match that portion of the identification with a corresponding portion of its own identification. If the portions of identification do not match, no further processing of the rema
Cook Carmen C.
GWcom, Inc.
Kwok Edward C.
Maung Nay
Skjerven Morrill & MacPherson LLP
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