Multiplex communications – Communication over free space – Having a plurality of contiguous regions served by...
Reexamination Certificate
1999-08-26
2003-06-17
Maung, Nay (Department: 2681)
Multiplex communications
Communication over free space
Having a plurality of contiguous regions served by...
C370S349000
Reexamination Certificate
active
06580704
ABSTRACT:
FIELD OF THE INVENTION
This invention relates, generally, to the field of telecommunications including wireless local area networks (WLANs) and, more particularly, to access point (AP) controlled WLAN systems which can facilitate communication directly between two mobile terminals having the same AP.
BACKGROUND OF THE INVENTION
Wireless local area networks (WLANs), constituted by a plurality of mobile terminals (mobile stations) such as mobile (cell) phones, notebook (laptop) computers which are facilitated with WLAN PC cards, and the like, communicate among themselves as well as through a network server, the network server providing support for communication between mobile terminals in different service sets (service areas) which are associated with different access points (APs). Such networks allow mobile terminals to be moved within a particular service area without regard to physical connections among the mobile terminals within that service area. An example of a model conforming to that developed by the IEEE 802.11 Committee is illustrated in
FIG. 9
of the drawings. (Discussion of the IEEE 802.11 model for WLAN architectures is found on pages 442-443 of the text
Data and Computer Communications,
5th Ed., by Wm. Stallings, published 1997 by Prentice-Hall, Inc.) Typically, all messages being transmitted among the mobile terminals of the same cell (same AP) in such WLAN schemes must be transmitted to the access point (AP) rather than being directly transmitted between the mobile terminals. Such centralized wireless communication provides significant advantages in terms of simplicity of the communication linkup as well as in power savings. However, such indirect communication between a pair of mobile terminals within a same AP also results in a bottleneck in that AP, noting that all the messages between any two stations within an AP service set must first be received by that AP and then be retransmitted to a destination point. Undesirably, this results, also, in the consumption of valuable communication bandwidth which also leads to an undesirable slowdown, especially when there exists a large number of mobile terminals within an AP service area.
For Direct Mode (DM) communication between two mobile terminals (MTs) in access point (AP) controlled WLAN systems to be successful, both MTs (1) have to be able to support DM, (2) they have to be associated to the same AP and (3) be able to create a wireless radio link with feasible (i.e., satisfactory) transmission power level. However, an underlying problem has existed in achieving this. Namely, there has been a problem of how the MTs as well as the associated AP know with certainty whether both of those MTs can have a DM radio linkup with a satisfactory transmission level prior to completion of the DM connection setup. (Direct Mode [DM], as referred to in the present application, means a Direct Mode communication linkup in which a direct or straight communication is effected between two MTs within the same AP service set of an AP controlled WLAN system.) Further, there has also been an underlying problem of how the initiating MT is able to create a DM connection to a remote, second MT of the same AP service area since the local unique identifier (LUI), which is generated by the AP to identify each MT associated with that AP, is not known by the other, remote MT. Any attempt at overcoming these problems must necessarily consider the following related issues: complexity, security, processing resources as well as channel usage.
The calibration scheme proposed by Sony International Europe as HL14SON2a, in the ETSI EP Bran (European Telecommunications Standards Institute EP Broadband Radio Access Network) No. 14 Conference, on July 1999, and incorporated herein reference, is based on a topology map stored in the AP computer which is to be used for finding out which MTs associated with that AP are feasibly located to permit DM communication. Such a topology map as that featured in HL14SON2a, July 1999, is presently illustrated as reference numeral
100
in
FIG. 10
of the drawings with regard to a showing, in the discussion which follows, of the impracticality as well as the security concerns that would be raised in using such a topology map to effect a DM communication setup between two MTs.
The basic concepts of the Standard, as previously proposed in HL14SON2a, is to ascertain the network topology associated with an AP via a calibration mechanism. Each MT associated to the same AP, according to that proposal, performs received signal strength (RSS) measurements with respect to all other ones of the MTs of that AP and reports them to the AP. Once all MTs have reported their measurement results to the corresponding AP, the AP creates and stores a topology map of that network. Such a topology map as that illustrated in
FIG. 10
of the drawings indicates the quality and connectivity between each MT with all other MTs associated with the same AP. Based on such a connectivity map as that illustrated in
FIG. 10
of the drawings, a connection setup for a Direct Mode (peer-to-peer) session can be performed through coordinating the three key elements, namely, the two MTs which are to be included in DM connection as well as the associated AP. In order to facilitate such a radio communication hookup, the example given in HL14SON3A, also presented in the ETSI EP BRAN No. 14 conference of July 1999, is applicable in connection with achieving a regulated transmit power level for each MT, independent of the transmit power associated with the other MTs of that AP. The HL14SON3A proposal submitted in connection with the HIPERLAN/2 Standard is also incorporated herein by reference.
Regarding the addressing problem, referred to earlier, no solutions have yet to be proposed which are directed, especially, to DM communication in AP controlled WLAN systems, based on the inventors' knowledge. Also, the typical way of distributing data in WLAN systems is to broadcast information for all MTs periodically or to maintain a mapping list from the local unique identifiers (LUIs) which correspond to the higher layer addresses associated with each AP. (The higher layer addresses are typically internet protocol (IP) addresses or Ethernet addresses, mobile phone numbers, and the like.) In the above-noted HL14SON2a proposal (HIPERLAN2 proposed Standard), there exists a master/slave situation, in which the AP is always the master and MT is the slave. Since AP is dynamically associating/disassociating medium access control identifiers (MAC-Ids) to joining/leaving MTs, it becomes paramount, at least for security reasons, that the AP should be the only entity or player in any communication linkup within the network which has specific knowledge about the MAC-Id mapping within its cell. Spreading or loosely channeling such information to the MTs poses questions of the security of the network. To avoid such problem, only MTs which are assigned to the same cell (same AP) and which are involved in DM communication linkup, the inventors submit, should actually have the right to ask for the corresponding MAC-Id address of another MT in order to initiate a DM connection.
Considering that the information is being broadcasted via wireless radio channel, the topology map (as proposed in HL14SON2a) as well as the broadcasting of the addressing information (from the higher layer address associated with the corresponding MAC-Id) have a bottlenecking effect on channel usage. Such negative impact on channel usage is especially evident during the periodic calibration phase. Since not all of the MTs may support DM communication and since DM communication is effected rather infrequently (e.g., once per hour, maybe), broadcasting of the RSS and addressing information as well as effecting the calibration within a period which is short enough for purposes of updating the data has a deleterious effect on the capacity of the radio channel during such times.
With regard to the topological map shown in
FIG. 10
of the drawings, which relates to the Sony contribution of the
Kuntze Roland
Salokannel Juha
Wellig Armin
Gelin Jean A
Maung Nay
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