A Cross-Layer Analysis Of Wireless Adaptive Multicast System

Along with wireless communication development, "one-to-many" transmission such as Mobile TV, videoconference pose strong challenges to tradition "one-to-one" transmission. Multicast is a "one-to-many" transmission method, which can make use of the finite spectrum resource, satisfy resource sharing of multicast group. With variable code, variable power and variable rate, adaptive modulation and coding can provide high throughput by choosing different modulation methods decided by channel condition. Communication mode of traditional layered model is fixed; Communication is also taken under the worst situation, which is suitable for wireless communication. Applying the cross-layer design for one-to-many multicast transmission, raising flexibility of multicast system, reducing bandwidth demands is an inevitable tendency in the next generation communication systems.A cross-layer design of adaptive wireless multicast transmission is studied in this paper. The main researches and contributions are as follows:1. In this paper, the principles of transfer characteristic in wireless environment, adaptation of modulation, and multicast are first introduced. Two typical algorithms for adaptive modulation are analyzed.2. A cross-layer design combined adaptive technique in physical layer and HARQ in data link layer of wireless multicast transmission is proposed which improves the spectral efficiency under the given delay and error performance constraint. The curve fitting method of packet error rate is used to compute the adaptive threshold. The closed-form expressions of the average spectral efficiency of multicast transmission in cross-layer design and layered design had been derived.3. With Matlab software, a simulation of adaptive wireless multicast system is taken to verify the closed-form expressions. The performance of unicast and multicast is simulated under different parameters. Simulate results also show this cross-layer design we proposed improve the spectral efficiency obviously comparing to the layered design with a little delay.