A method and system are provided for detecting messages using enhanced distributed signaling for a wireless communication network. The method describes a framework in which a set of participating wireless stations work cooperatively to improve the efficiency and reliability of the wireless communication network. It is understood that the wireless stations may include both mobile terminals and fixed terminals such as base stations.
In a wireless communication network, the radio signal received by a wireless station is a noisy copy of the original signal sent by the transmitting wireless station. The natural environmental parameters, such as weather and vegetation, and man-made environmental parameters, such as buildings, impair the integrity of the radio signals. In other words, the received signal is an impaired copy of the original signal. The impairment of the radio signal reduces the data rate of the wireless network or renders the signal unrecognizable by the wireless receiver.
Low data rate at the edges of a cell in a wireless network and the existence of blind spots are widespread problems in almost all deployments of fixed or mobile wireless networks, regardless of the communication standards. Specifically, these problems are mostly due to the propagation impairment of the radio such as path loss, geographical obstacles, and deleterious effects of a radio environment.
Multiple-antenna transmission and the reception method is one of the methods that improve the reliability of the wireless communication network in hostile wireless environments through the adoption of spatial diversity. Spatial diversity primarily enhances the throughput at cell edges. Unfortunately, in some wireless applications, such as ad hoc and sensor networks, it is not feasible to deploy multiple antennas due to the size, cost, and power limitations.
The statistically independent channel condition that the wireless stations experience is a valuable source of spatial diversity. By incorporating spatial diversity, a wireless communication network that adopts the enhanced distributed signaling method creates a virtual multiple-antenna wireless transmission system with multiple single antenna wireless stations.
For a single-antenna wireless station with limited computational resources, the wireless communication network with enhanced distributed signaling offers transmission diversity that improves the throughput of the participating wireless stations. For a set of wireless stations, each of which has various levels of resource constraints, the enhanced distributed signaling method improves the performance of the wireless network with or without synchronization among all the single-antenna wireless stations.
In the wireless network with the enhanced distributed signaling method, each of the participating single antenna wireless stations act as a proxy for its peers. When a source wireless station sends a message to a destination wireless station, the radio signal that carries the message is sent to all participating wireless stations. Each participating wireless station in turn sends a supplementary signal on behalf of the source wireless station to the destination wireless station. The destination wireless station then processes the multiple noisy copies of the original signal to retrieve the original message.
The enhanced distributed signal method disclosed herein a framework for the wireless communication network with a distributed signaling method. The disclosed framework builds on the conventional distributed signal method that improves the overall system performance.
One example of a conventional distributed signal wireless communication network is a two-phase detect-and-forward system. In the conventional two-phase detect-and-forward system, a wireless station receives Ũi, a noisy copy of the original signal Ui from its participating peer i in the first phase. In the second phase, the participating wireless station sends its own signal, together with the noisy signal Ũi detected in the first phase, to the destination wireless station. In other words, the proxy wireless station re-transmits the noisy signal received from its peer to the destination wireless station without further processing.
One exemplary scenario of a three-node system with the detect-and-forward method, where wireless stations 1 and 2 participating in the distributed signaling method sends messages to wireless station 3, is described below.
In the first phase, wireless station 1 transmits signal U1 and wireless station 2 transmits signal U2. Wireless station 1 receives signal Ũ2, wireless station 2 receives signal Ũ1, and wireless station 3 receives (1, 2).
In the second phase, wireless station 1 re-transmits Ũ2, wireless station 2 re-transmits Ũ1, and wireless station 3 receives
            (        ⁢                            U          ~                …            1        ,                              U          ~                …            2        ⁢                  )            .      After receiving (1, 2) and
            (        ⁢                            U          ~                …            1        ,                              U          ~                …            2        ⁢          )        ,wireless station 3 processes
            (        ⁢                            U          ~                …            1        ,                              U          ~                …            1        ⁢          )        ⁢                  ⁢    and    ⁢                  ⁢          (        ⁢                            U          ~                …            2        ,                              U          ~                …            2        ⁢          )      jointly and retrieves the original messages sent by wireless station 1 and 2. If Ũ2 is sent, then it is amplify-and-forward.
The disclosed invention discloses a framework that is applicable to all types of wireless communication networks. One example is a centralized wireless communication network where some users might be out of reach of the base station, particularly in uplink transmission. If any wireless station experiences low throughput due to geographical obstacles or random fluctuations of the wireless channel, the disclosed signaling method brings higher throughput to all the participating wireless stations.
Another example is a wireless communication network where the wireless stations have limited transmit power, such as wireless handset or handheld devices. In this case, the wireless handset or handheld device, under the supervision of the base station can participate in the enhanced distributed signaling method described above and improves the throughput and reliability of all the participating wireless handheld devices.
The conventional distributed signaling method is based on a single-user coding method. The enhanced distributed signaling method disclosed herein introduces the concept of joint coding and signaling design for a set of network nodes in a wireless communication network. Under the framework of cooperative transmission of signals, each of the wireless stations participating in the enhanced distributed signaling method works as a single wireless transmission station and the destination wireless station decodes the received signals jointly.
The disclosed enhanced distributed signaling method not only incorporates the conventional coding methods but also supports for example, concatenated coding and cross layer schemes in physical and medium access layers.