Patent Application
20060172756
Known wireless network systems (e.g., 802.11 wireless networks) generally operate in two distinct modes: infrastructure and ad hoc (e.g, peer-to-peer). In the infrastructure mode, mobile units may communicate with other mobile units within the wireless network via an access point (“AP”). In the ad hoc mode, mobile units may communicate with one another directly.
The known wireless network systems have several shortcomings. For example, each mobile unit often transmits at the same high power level regardless of its proximity to the AP and therefore-wastes power and causing interference. In addition, cooperation between mobile units residing in the same wireless network is often limited. Therefore, there is a need for an improved wireless network architecture.
The present invention relates to a system and method for clustering mobile devices in a wireless network. The system includes a wireless access point (“AP”) and a plurality of mobile units (“MUs”). Each of the MUs has a wireless transducer. At least two MUs of the MUs are grouped, based on a predetermined parameter, into a cluster which included a head MU and at least one member MU. Communications between the at least one member MU and the AP are conducted via the head MU.
Disclosed is a system and method for clustering mobile devices in a wireless network. In particular, the present invention relates to an improved wireless network architecture that, for example, uses location information of mobile units to form clusters of mobile units.
The system 100 may include a number of mobile units (“MUs”), e.g., MUs 41-45 and 51-54. The MU may be any mobile unit and/or networking device (e.g., a network node) known to those of ordinary skill in the art which includes a wireless transducer. For example, the MU may be a portable barcode scanner, a mobile phone, a two-way pager, PDA, etc. Each MU may communicate with the wireless network 10 via an AP (e.g., AP 30) of the wireless network 10. As described below, each MU may also communicate with the wireless network 10 via another MU.
Two or more MUs may be grouped into a cluster based on a plurality of factors such as geographical proximity to one another, an internal load level, a battery level, a hardware configuration, etc. For example, the MUs 41-45 may be grouped into a cluster 40 and the MUs 51-54 may be grouped into a cluster 50. In preferred embodiment of the present invention, each cluster includes one cluster-head MU and at least one cluster-member MU. For example, the cluster 40 may includes the cluster-head MU 41 and the cluster-member MUs 41-45. Similarly, the MU 51 may be the cluster-head of the cluster 50 and the MUs 51-54 are the cluster-member MUs. In each cluster, a cluster-member MU communicates with the cluster head MU using, e.g., IEEE 802.11 technology; the cluster-head MU communicates with the AP using, e.g., IEEE 802.11 and/or 802.16 (WiMAX) technology. In an alternative exemplary embodiment of the present invention, the cluster may include two or more cluster-head MUs; or the cluster may further be subdivided into a plurality of sub-clusters, each sub-cluster having a structure similar one of the cluster.
As one of ordinary skill in the art will understand, the cluster may be dynamically changing its membership. For example, the membership of a particular cluster may continuously change depending on the relative locations of its MUs. As shown in
In step 201, the system 100 may determine locations and/or relative locations of the MU's in communication with the wireless network 10. The system 100 may use any real time location system or any other methods known to those of ordinary skill in the art. For example, the system 100 may employ a Received Signal Strength Indication (“RSSI”) method. The server 20 may generate and transmit a signal via one or more APs (e.g., APs 30 and/or 35). Each MU may then transmit a response signal to the APs 30 and/or 35. The APs 30/35 may receive the response signal and forward it to the server 20. The server 20 may then utilize the intensity of the response signal(s) and compare it with predetermined geographically marked locations or points (e.g., within the wireless network 10 coverage area) to determine the relative locations of the MUs (e.g., the MUs 41-45 and 51-54).
The system 100 may, alternatively, or in combination, employ a Time Difference Of Arrival (“TDOA”) method to determine the relative locations of the MUs (step 201). For example, the server 20 may generate and transmit a signal to the MUs via at least one of the APs 30 and/or 35. The MUs may each transmit a response signal to the wireless network 10 via at least two APs (e.g., APs 30/35). The APs 30/35 may then forward the response signals to the server 20. The server 20 may utilize the TDOA method using response signals at each AP 30/35 and compare them to determine the precise location of each MU.
In step 203, the server 20 may group the MUs into clusters based on a plurality of factors mentioned above. In a preferred embodiment, the server 20 may cluster MUs based their location (e.g., within the range of the wireless network 10); the server 20 also determines/designates a cluster-head MU. As shown
As one of ordinary skill in the art will understand, steps 201 and 203 may be repeated at any time interval or upon request by a user. Therefore, the MUs included in a cluster and/or the cluster-head MU may change over time. For example, in the wireless network 10 where the MUs are continuously changing location, the system 100 may determine the locations of the MU's (step 201) and cluster the MUs (step 203) at a short interval (e.g., every few minutes). In the wireless network 10 where the MUs are fixed in location or have limited mobility, the system 100 may repeat steps 201-203 only upon user request or at a prolonged interval (e.g., every 48 hours).
In step 205, one or more cluster-member MUs generate a packet for transmission. For example, the cluster-member MU 43 generates a packet for transmission to the wireless network 10. The cluster-member MU 43 transmits the packet to the cluster-head MU 41 (step 207); the cluster-head MU 41 may then transmit (e.g., relay) the packets the wireless network 10 via the AP 30 (step 209). Other cluster-member MUs (e.g., MUs 42, 44, 45) may, at the same or different times, also transmit a packet to the cluster-head MU 41 for further transmission. For example, the cluster-head MU 41 may receive multiple packets from the cluster-member MUs and may aggregate the multiple packets to fewer (e.g., one) packets for transmission to the wireless network 10. As one of ordinary skill in the art will understand, such aggregation of packets may result in decreased congestion and/or interference in the wireless network 10 and less overhead.
In step 211, the cluster-head MU 41 may receive a response signal from the wireless network 10 via the AP 30. The cluster-head MU 41 may determine to which one of the cluster-member MUs 42-45 of the cluster 40 the transmission is intended and transmit the response signal (e.g., packet) to the corresponding MU (e.g., the MU 43) (step 213).
The present invention provides several advantages over known communication systems and methods of communication in wireless networks. As described above, data transmission to and from the cluster-member MUs in a cluster may be relayed through a cluster-head MU. Therefore, the cluster-member MUs may operate at a reduced power level.
The system and method of the present invention also allow for multiple simultaneous transmissions via the aggregation of packets from the cluster-member MU's. For example, MU 42 may communicate with the MU 41 and, at the same time—i.e., simultaneously, the MU 53 may communicate with MU 51. Furthermore, the rotation (e.g., steps 201-203) of cluster-head MUs in a cluster may result in increased throughput and longer battery life in the MUs.
Embodiments of the present invention also include the benefit of relaying “unheard” packets from distant MUs, thus resulting in better resource utilization. In other words, a cluster-member MU which otherwise is unable to communicate with the AP (e.g., because of its location outside of the AP's range), may now communicate with the AP via the cluster-head MU.
The present invention has been described with reference to an embodiment having the MUs 41-45 and 51-54, the wireless network 10, and the APs 30 and 35. One skilled in the art would understand that the present invention may also be successfully implemented, for example, for any number of MUs, APs, and/or a plurality of the wireless networks 10. Accordingly, various modifications and changes may be made to the embodiments without departing from the broadest spirit and scope of the present invention as set forth in the claims that follow. The specification and drawings are accordingly to be regarded in an illustrative rather than restrictive sense.
