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To improve the efficiency of field test, a new integrated wireless test ring (T-Ring) system is planned to be established. In this system, the cell radius will be proportionally reduced. To study the vertical handoff between WLAN and cellular networks of the T-Ring system, we need to analyze vertical handoff quantitatively. Based on the analysis result, the corresponding parameters will be adjusted to make the test system equivalent with the realistic system. Vertical handoff probability and handoff blocking probability are the two most important parameters which characterize the vertical handoff. We derive the close form of these two parameters for WLAN-first handoff scheme. To guarantee these parameters equivalent with those of the realistic system, speed of the mobile user and average load of the cellular networks should be adjusted with the cell size. A method of parameter adjustment is proposed by numerical calculation and theoretical analysis. Simulation results show that our method is precise enough. The analysis result is also applicable to other realistic micro cells systems.

In multi-source multi-relay wireless network, centralized relay selection schemes are difficult to realize because they usually require global information, which is hardly available due to the limited memory and latency in realistic systems. Meanwhile, in classical distributed relay selection schemes, each source selects its “best” relay merely based on the local channel information. However, such schemes may lead to the case that several sources simultaneously select the same “best” relay and therefore causes a bottleneck problem. In this paper, we propose an opportunistic distributed relay selection scheme. In this scheme, each source selects its “best” relay by jointing the channel information and local “topology” information which can greatly ease the bottleneck problem. We also propose a three-step distributed signal interaction protocol by which every source can acquire its local “topology” information. Finally, we show the advantages of our proposed scheme by comparing the simulation results with other methods.

Many measurement studies showed that network traffic usually exhibits self-similar nature, meanwhile, wireless fading channels lead to the time-variant service rates of network nodes. Compared with classical queuing systems with Markov sources or constant service rates, the queuing system with self-similar input in a wireless fading channel is more complicated, and it is very difficult to obtain closed-form formulas for the queuing performances. In this paper, we analyze the queuing behavior with self-similar traffic input in Rayleigh fading channel by establishing a queuing system model, and present a convenient and efficient algorithm to estimate the queue length distribution. Simulation results validate the accuracy of the proposed estimation algorithm.

In this paper, we propose a multi-users cooperative communication scheme based on the network coding in GF(2n). Through changing the implementation of network coding and designing the proper coding coefficients, this network-coded cooperation in GF(2n) (NCCG) can improve the solvability of decoding set of equations in the receiver effectively and make full use of the advantages taken by network coding. Compared with the cooperation by resending and cooperation based on network coding with XOR operation, the analysis and simulation results indicate that NCCG can yield higher system diversity gain, improve the efficiency of cooperation and the performance of system powerfully.

This paper presents a novel network coding (NC) medium access control (MAC) protocol design, named NC-ALOHA. The basic idea of NC-ALOHA is completing the network coding process during one packet per slot at each transmitting terminal; the network coding coefficient vectors used by different transmitting terminals are orthogonal with each other. By virtue of network coding, traditional collision assumption is changed, so that more than one transmitting terminals could send packets at the same slot. Quantitative throughput analysis is conducted for NC-ALOHA protocol and its performance is verified by simulation. It is observed that significant throughput improvement and delay decrease can be achieved in comparison with slotted ALOHA protocol.

In this paper, a novel joint CDMA/RTDMA protocol for multimedia transmission in wireless networks is studied. In this scheme, the base station allocates terminals with code-slots instead of slots. Theoretical analysis of voice packet dropping rate and data delay are based on the M/M/n/m model and phase process respectively. Through simulation and numerical results, this new MAC protocol can provide multiple service QoS even under heavy load.