What is Mobile Computing Wireless Communication Systems Mobile

What is Mobile Computing? Wireless Communication Systems Mobile Communication Systems Architecture Key Technologies of Mobile Computing Applications

MOBILE COMMUNICATION SYSTEMS ARCHITECTURE PSTN & PLMN PCS Basic Architecture Cellular Wireless Communication

PSTN & PLMN 公眾電話交換網路(Public Switched Telephone Network， PSTN) 陸地行動電話網路(Public Land Mobile Network， PLMN)

PLMN is a network that is established and operated by an administration or by a Recognized Operating Agency (ROA) for the specific purpose of providing land mobile telecommunications services to the public Access to PLMN services is achieved by means of an air interface involving radio communications between mobile phones or other wireless enabled user equipment and land based radio transmitters or radio base stations

PLMNs interconnect with other PLMNs and Public switched telephone networks (PSTN) for telephone communications or with internet service providers for data and internet access 通話屬於同一PLMN的兩支手機，會在自己的PLMN中通話若一端為遠傳手機，另一端為中華電信的固接式電話，則須兩家電信公司合作，以接通電話

PCS基本架構無線電網路(Radio Network) 有線傳輸網路(Wireline Transport Network)

無線電網路(RADIO NETWORK) 手機不同系統使用不同名稱 AMPS：mobile phone Wireless Local Loop：subscriber unit PACS等低階系統：portable GSM：mobile station 用戶使用手機與個人通訊網路的基地台(Base 聯繫 Station，BS)

Antenna

Base Station

Cell sizes macro-cellular： 1 -30 km micro-cellular： 200 -2000 m pico-cellular： 4 -200 m femto-cellular：in residential or small business environments

註：MACROCELL Provides the main coverage in a mobile network The antennas for macrocells are mounted on ground-based masts, rooftops and other existing structures Must be positioned at a height that is not obstructed by surrounding buildings and terrain Base stations have a typical power output of tens of watts Communicate with phones up to about 35 kilometres (22 miles) distance

註：MICROCELL Provide infill radio coverage and additional capacity where there are high numbers of users within macrocells The antennas for microcells are mounted at street level, typically on the external walls of existing structures, lamp posts and other street furniture The antennas are smaller than macro cell antennas and, when mounted on existing structures, often blend in with building features to minimize visual impact

Typically, microcells provide radio coverage across smaller distances and are placed 300 m-1000 m apart They have lower outputs than macrocells, usually a few watts

註：PICOCELL Provides more localized coverage than a microcell Normally found inside buildings where coverage is poor or where there a high number of users airport terminals train stations shopping centers

註：FEMTOCELL Originally known as an Access Point Base Station A small cellular base station, typically designed for use in residential or small business environments Connects to the service provider’s network via broadband (such as DSL or cable); current designs typically support 2 to 5 mobile phones in a residential setting Allows service providers to extend service coverage indoors, especially where access would otherwise be limited or unavailable

Incorporates the functionality of a typical base station but extends it to allow a simpler, self contained deployment; for example, a UMTS femtocell containing a Node B, RNC and GSN with Ethernet for backhaul

Hierarchical Cell Structure

Hierarchical cell structure an operator can tailor-fit capacity to match traffic demands, and use the available frequency spectrum more efficiently mobile terminals moving at high speed are directed to macrocells hot spots with mobile terminals moving at low speed are covered by small cells (microcells and picocells)

CLUSTER SIZE AND FREQUENCY RE-USE DISTANCE Geometry of a hexagon (with cell radius 1 R) Surface area (SR) is 6 R 2 × =

Honeycomb (hexagonal) cell structure Cluster set of different frequencies used in group of cells cluster is repeated by linear shift i steps along one direction j steps in the other direction

i j D Distance between adjacent cell centers = × cell radius = R Reuse distance (D) distance between the centers of two co-channel cells D = where = -½ 餘弦定理

Cluster radius (Rc) = = R

Cluster size (K) number of channels needed for (i, j) grid K is proportional to surface area of cluster Surface area of one hexagonal cell is

SR = surface area of cell RC = cluster radius R = cell radius Surface area of a (hexagonal) cluster of K cells is Combining these two expressions gives

Possible cluster sizes we have seen and also thus K = i 2 + j 2 + ij with integer i and j

7 6 1 K = i 2 + ij + j 2 K= 22 + 2*1 + 5 12 7 K=4+2+1 K=7 2 6 j i 3 4 R 2 1 5 3 D D= 3 K * R D = 4. 58 R Frequency re-use distance (D) is based on the cluster size (K)：