Dynamic Ranging Codes Allocation Scheme in IEEE 802.16e Networks

IEEE 802.16e is a rapidly developing standard with high transmission rates, wide cover ranges, and the ability to support users moving at high-speed. This standard adopts code division multiple access (CDMA) as the multiple access protocol. It utilizes 256-ranging codes and allocates these 256 ranging codes to four types of messages. When the mobile station (MS) is ready to send a message to the base station (BS), it will select a ranging code, among the ranging codes allocated to that message, to transmit to BS. After receiving this ranging code, BS will find out what the corresponding message is by reading the value of this ranging code. BS will then execute the corresponding responses. Although the standard provides parameters to allow the BS to determine the numbers of ranging codes allocated to each message, it does not describe how to determine the number of ranging codes allocated to each message. Therefore, in this paper we will propose a scheme to calculate and allocate the appropriate numbers of ranging codes to these four messages. It was verified by simulations that this proposed scheme can indeed reduce the probability of occurrence of collisions and improve the overall network performance.