Perrella Stephen 3/1/01 Wireless Networks Written Assignment # 2 The AMP System v. the GSM System Before choosing either the Advanced Mobile Phone System described in class and the Global System for Mobile Telecommunications illustrated in the IEEE Communications Magazine article entitled, "Overview of the GSM System and Protocol Architecture," the background and implementation of each system must be analyzed and understood. Each system has their positive aspects as well as their negative ones. These positive and negative aspects must be weighed with respect to the needs of the systems users in order to select the right system for the situation. In the Advanced Mobile Phone System (AMPS), there is an analog signal processing at the sender side. The AMPS signal processing has five components. First, there is the compress of the AMPS system that reduces the dynamic range of human speech by a factor of 2 and restores this noise at the other end of the system. Next, there is the pre-emphasis filter that amplifies higher frequencies that tend to be weaker. Third, the limiter limits amplitude so that frequency deviation is within 12 kHz on either side. Also, the low-pass filter attenuates signal components at frequencies of 3 kHz or above. Finally, the AMPS SAT helps in identifying the base station and the strength of the signal. The channels of an Advanced Mobile Phone System range from logical channels to voice and traffic channels. The logical channels include a control channel to establish a call. The voice and traffic channels are carries in one physical channel and the AMPS
uses bland-and-burst mode to share the traffic from these two logical channels. The system interrupts the flow of user conversation and transmits the control message for approximately 100 ms.. This process is called in-band signaling. The Global System for Mobile Telecommunications represents the European standards for mobile telecommunication. The services, functional and subsystem interfaces are all of worldwide standards. GSM provides terminal mobility along with personal mobility provided through the insertion of a subscriber module identity (SIM) into the GSM network. Generally, GSM may be viewed as a framework for studying the functions and issues that are specific to cellular type personal communication networks, whatever the implementation might be. GSM defines a number of network databases that are used in performing the functions of mobility management and call control in a public land mobile network, better known as PLMN. These elements include the location registers consisting of the home location register (HLR), the visiting location register (VLR), the equipment identity register (EIR), and the authentication center (AC). The HLR maintains and updates the mobile subscriber's location and his or her service profile information. The VLR maintains the same information locally, where the subscriber is roaming. The VLR is defined as a stand-alone function, but is usually viewed by vendors as part of the MSC. These registers are called service control points (SCP) in the terminology used in intelligent networking (IN). The EIR is used to list the subscribers' equipment identities, which are used for identification of unauthorized subscriber equipment, and hence denial of service by the network. The AC provides the keys and algorithm for maintaining the security of subscriber id...