【導讀】導下進行的研究工作及取得的成果。盡我所知，除文中特別加以標注和致。含我為獲得及其它教育機構的學位或?qū)W歷而使用過的材料。明并表示了謝意。以贏利為目的前提下，學?？梢怨颊撐牡牟糠只蛉績?nèi)容。移動通信的網(wǎng)絡覆蓋、容量、質(zhì)量是運營商獲取競爭優(yōu)勢的關鍵因素。網(wǎng)絡容量、網(wǎng)絡質(zhì)量從根本上體現(xiàn)了移動網(wǎng)絡的服務水平，是所有移動網(wǎng)絡優(yōu)化的主題。計出來的，它是在蜂窩系統(tǒng)的基礎上發(fā)展而來的。隨著移動通信的普及，GSM系統(tǒng)已經(jīng)

　　

【正文】 ion controllers (BSCs) and the base transceiver stations (BTSs). BSC— The BSC provides all the control functions and physical links between the MSC and BTS. It is a highcapacity switch that provides functions such as handover, cell configuration data, and control of radio frequency (RF) power levels in base transceiver stations. A number of BSCs are served by an MSC. BTS— The BTS handles the radio interface to the mobile station. The BTS is the radio equipment (transceivers and antennas) needed to service each cell in the work. A group of BTSs are controlled by a BSC. The Operation and Support System The operations and maintenance center (OMC) is connected to all equipment in the switching system and to the BSC. The implementation of OMC is called the operation and support system (OSS). The OSS is the functional entity from which the work operator monitors and controls the system. The purpose of OSS is to offer the customer costeffective support for centralized, regional, and local operational and maintenance activities that are required for a GSM work. An important function of OSS is to provide a work overview 21 and support the maintenance activities of different operation and maintenance anizations. Additional Functional Elements Other functional elements shown in Figure 2 are as follows: message center (MXE)— The MXE is a node that provides integrated voice, fax, and data messaging. Specifically, the MXE handles short message service, cell broadcast, voice mail, fax mail, , and notification. mobile service node (MSN)— The MSN is the node that handles the mobile intelligent work (IN) services. gateway mobile services switching center (GMSC)— A gateway is a node used to interconnect two works. The gateway is often implemented in an MSC. The MSC is then referred to as the GMSC. GSM interworking unit (GIWU)— The GIWU consists of both hardware and software that provides an interface to various works for data munications. Through the GIWU, users can alternate between speech and data during the same call. The GIWU hardware equipment is physically located at the MSC/VLR. 4. GSM Network Areas The GSM work is made up of geographic areas. These areas include cells, location areas (LAs), MSC/VLR service areas, and public land mobile work (PLMN) areas. The cell is the area given radio coverage by one base transceiver station. The GSM 22 work identifies each cell via the cell global identity (CGI) number assigned to each cell. The location area is a group of cells. It is the area in which the subscriber is paged. Each LA is served by one or more base station controllers, yet only by a single MSC (see Figure 4). Each LA is assigned a location area identity (LAI) number. An MSC/VLR service area represents the part of the GSM work that is covered by one MSC and which is reachable, as it is registered in the VLR of the MSC. The PLMN service area is an area served by one work operator. 5. GSM Specifications Before looking at the GSM specifications, it is important to understand the following basic terms: bandwidth— the range of a channel39。s limits。 the broader the bandwidth, the faster data can be 23 sent bits per second (bps)— a single onoff pulse of data。 eight bits are equivalent to one byte frequency— the number of cycles per unit of time。 frequency is measured in hertz (Hz) kilo (k)— kilo is the designation for 1,000。 the abbreviation kbps represents 1,000 bits per second megahertz (MHz)— 1,000,000 hertz (cycles per second) milliseconds (ms)— onethousandth of a second watt (W)— a measure of power of a transmitter Specifications for different personal munication services (PCS) systems vary among the different PCS works. Listed below is a description of the specifications and characteristics for GSM. frequency band— The frequency range specified for GSM is 1,850 to 1,990 MHz (mobile station to base station). channel separation— The separation between adjacent carrier frequencies. In GSM, this is 200 kHz. modulation— Modulation is the process of sending a signal by changing the characteristics of a carrier frequency. This is done in GSM via Gaussian minimum shift keying (GMSK). transmission rate— GSM is a digital system with an overtheair bit rate of 270 kbps. access method— GSM utilizes the time division multiple access (TDMA) concept. TDMA is a technique in which several different calls may share the same carrier. speech coder— GSM uses linear predictive coding (LPC). The purpose of LPC is to reduce the bit rate.. Speech is encoded at 13 kbps.