Contention vs. Polling in wireless high-bit-rate packet transfer for fast movers in connected micro-cells

For high-speed packet transfer in the wireless environment, the shared radio medium is provided to mobile terminals (MT) through the control of MAC layer. Contention and polling technique are known as two fundamental methods that are used in this environment. This paper aims to compare the operation of these two methods if they are enhanced to use in a connected micro-cells system to support for high-bit-rate packet transfer for fast movers. Consider them in capability of offering smooth handover in term of maintaining handover latency, guaranteeing acceptable delay for multimedia traffic, transmitting over randomly varying wireless channel, the authors realize that polling technique can satisfy these demands but not contention. According to this analysis, we propose the multi polling and virtual single cell to make packet transfer from/to MT to BS (base station) even during handover kept in a stable condition without latency. To create the virtual single cell, we configure an LMC (Logical Macro-Cell) which groups several adjacent micro-cells and the serving cell into the same multicast tunnel. BS of each LMC sends polling packet with the same sequence number to the identical target terminal and the target terminal responds only to the BS of the micro-cell where it stays. Mobile terminal (MT) can conduct packet transfer if it stays in the LMC in spite of quick cell-to-cell move. The LMC is switched over to the next LMC when the MT moves to another micro-cell. Two LMCs can be a virtual single cell since LMC switchover occurs when the target terminal stays in a cell shared by two adjacent LMC. To do so, the total micro-cells in which the target terminal moves as if they are virtually single cell for the target terminal, and this allows high-bit rate packet transfer to fast terminals. Our simulation results outperform in handover latency though somewhat overhead induced. KeywordsContention, Polling, connected micro-cells , Logical Macro-cell, multi polling.