Cellular Networks and Wireless Communication Systems Quiz

Principles of Cellular Networks and 2G Network Standards

• Wireless networks are classified based on coverage area into different categories including WWANS, WMANS, WLANS, and WPANS.

• Cellular networks are a revolutionary development in telecommunications and support locations not easily served by wireless networks or WLANs.

• Cellular networks use multiple low-power transmitters, and areas are divided into cells each served by its own antenna and base station consisting of transmitter, receiver, and control unit.

• Adjacent cells are assigned different frequencies to avoid interference or crosstalk, and the objective is to reuse frequency in nearby cells.

• Approaches to cope with increasing capacity include adding new channels, frequency borrowing, cell splitting, cell sectoring, network densification, and interference coordination.

• The Advanced Mobile Phone Service (AMPS) was the first 1G analog wireless network that included two 25-MHz bands allocated to AMPS, one for transmission from base to mobile unit and one for transmission from mobile unit to base.

• Second-generation systems are digital and provide encryption, error detection and correction, and dynamic channel access.

• Global System for Mobile Communications (GSM) uses the FDMA/TDMA approach and is developed to provide a common second-generation technology for Europe.

• GSM subscriber units are generic until SIM is inserted, and SIMs roam, not necessarily the subscriber devices.

• The IS-95 standard is the most widely used CDMA cellular standard, used mainly in North America, and consists of forward link channels and reverse link channels.

• The forward link channels support pilot, synchronization, paging, and traffic channels, while the reverse link consists of up to 94 logical CDMA channels.

• Mobile radio propagation effects include signal strength and fading, and handoff performance metrics include handoff blocking probability, handoff probability, rate of handoff, interruption duration, and handoff delay.Overview of Cellular Wireless Systems: 1G to LTE-Advanced

• Cellular wireless systems have evolved from 1G to 2G, 3G, and now LTE-Advanced

• 1G systems were analog, while 2G systems such as GSM introduced digital voice and SMS

• GPRS and EDGE were introduced as part of 2.5G, providing a datagram switching capability and higher data rates

• 3G systems such as CDMA2000 and WCDMA provided higher data rates, support for packet-switched and circuit-switched data services, and more efficient use of spectrum

• LTE and LTE-Advanced, known as 4G, offer ultra-mobile broadband access, peak data rates up to 1 Gbps, and support for multimedia applications

• LTE uses bearers for quality of service (QoS) control instead of circuits, with guaranteed bit rate (GBR) and non-GBR bearers

• Each bearer is given a QoS class identifier (QCI) and associated with standard forwarding treatments

• The evolved packet system (EPS) is the overall architecture for LTE, with the LTE RAN called E-UTRA and the core network called EPC

• EPC components include the mobility management entity (MME), serving gateway (SGW), packet data network gateway (PGW), and home subscriber server (HSS)

• Non-Access Stratum Protocols such as EPS Mobility Management (EMM) and EPS Session Management (ESM) manage mobility and connections between UE, SGW, and PGW

• LTE resource management includes service data flows (SDFs) to differentiate traffic types and EPS bearers to map to specific QoS parameters

• EPC functions include mobility management, inter-cell interference coordination (ICIC), and network access control and routing.Overview of LTE and LTE-Advanced Networks

• LTE is used for wireless communication over long distances such as cities or countries.

• Mobile phones use full-duplex communication.

• IEEE 802.11 standard is classified as a wireless LAN, while 4G cellular network is classified as a wireless WAN.

• WiMAX standard is classified as a wireless MAN.

• In cellular networks, cells are divided into a number of wedge-shaped sectors.

• LTE uses MIMO and OFDM, while LTE-Advanced includes carrier aggregation, MIMO enhancements, relay nodes, heterogeneous networks, and coordinated multipoint transmission and reception.

• LTE uses a hierarchical channel structure between the layers of the protocol stack, with user plane protocols such as PDCP, RLC, and MAC.

• LTE radio interface is divided into control plane and user plane.

• LTE uses three types of channels: logical channels, transport channels, and physical channels.

• LTE-Advanced aims to cater for services with diverse requirements and includes key enabling technologies such as SDN and NFV.

• 5G network will have several deployment scenarios and will include software-defined network (SDN) and network function virtualization (NFV).

• The GSM Association specifies services beyond voice, such as video calls, instant messaging, chat, and file transfer in what is known as the Rich Communication Services (RCS).Wireless Communication Networks Review Questions

• The methods to improve coverage and capacity in cellular systems include cell sectoring, cell splitting, and frequency borrowing.

• Cell splitting involves splitting cells in areas of high usage into smaller cells.

• Paging is the step when the MTSO sends a message to certain BSs to find the called mobile unit.

• Call blocking probability is the probability of a new call being blocked due to heavy load on the BS traffic capacity, while call dropping probability is the probability that a call is terminated due to a handoff.

• Handoff blocking probability is the probability that a handoff cannot be successfully completed.

• GPRS enhanced GSM by providing a datagram switching capability and allowing users to open a persistent data connection.

• The classes of wireless networks include cellular, ad-hoc, and satellite networks.

• Cellular network organization involves dividing the coverage area into smaller cells, and a hexagonal pattern is chosen for cellular networks due to its uniformity and minimal overlap.

• Frequency reuse involves reusing frequencies in different cells to increase capacity and reduce interference.

• The principal elements of a cellular system include mobile stations, base stations, and a mobile switching center.

• Handoff is the process of transferring a call from one cell to another, and handoff performance metrics include handoff failure rate, handoff delay, and call dropping probability during handoff.

• CDMA offers advantages for cellular systems such as increased capacity, improved voice quality, and better security. The most prevalent standards of 3G mobile networks include CDMA2000 and WCDMA.