W-CDMA. WCDMA makes use of many core CDMA technologies created by Qualcomm.

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1 W-CDMA W-CDMA is a standard found in 3G mobile communication network..air interface for 3G mobile networks. -provides voice, text and multimedia Messaging Service(MMS) -provides increased data transimission rates. -supports both frequency Division and Time Division Duplex(TDD) multiplexing. WCDMA stands for Wideband Code Division Multiple Access and is the 3G technology defined by the ITU's IMT WCDMA makes use of many core CDMA technologies created by Qualcomm. WCDMA networks and devices are not compatible with regular CDMA networks and devices. they merely share some of the same core technologies. QoS classes 1.conversational class -this class applicable on aaplications involving real time communivation such as use of video conferencing. -minimum quality requirements for speech are clarity of speech,low jitter and low delay. -requires synchronize media streams. 2.Streaming class -This class used in applications where information is exchanged between two users. -example o applications are web radio,nes streams and VOD. The quality requirements are low jitter and media synchronization. -This class uses buffering techniques 3.Interactive class This class ia applicable on applications that cover both human and machine communication with another device. -examples of such applications include games and web browsing. -minimum quality requirements in this case are round trip delay and tolerance to packet loss. 4.Background class -This class is applicable on all the applications that obtain data but do not ned to handle the data immediatly. -examples include s and SMS. -The minimum quality requirement is data integrity

2 Parameters and attributes defined by UMTS Traffic class ('conversational', 'streaming', 'interactive', 'background') Maximum bit rate (kbps) Guaranteed bit rate (kbps) Delivery order (y/n) Maximum SDU size (octets) SDU format information (bits) SDU error ratio Residual bit error ratio Delivery of erroneous SDUs (y/n/-) Transfer delay (ms) Traffic handling priority Allocation/Retention Priority Source statistics descriptor ('speech'/'unknown') SDU = Service Data Unit WLL-Wireless Local Loop -also called fixed wireless access. -offers two way communication servicesto users in small area. -I has replaced the wireline local loop technology. -Wireless local loop (WLL) is the use of a wireless communications link as the "last mile / first mile" connection for delivering plain old telephone service (POTS) or Internet access (marketed under the term "broadband") to telecommunications customers. Various types of WLL systems and technologies exist. Other terms for this type of access include Broadband Wireless Access (BWA), Radio In The Loop (RITL), Fixed-Radio Access (FRA), Fixed Wireless Access (FWA) and Metro Wireless (MW). WLL is a system that connects subscribers to the local telephone station wirelessly. Systems WLL is based on:cellular Satellite (specific and adjunct) Microcellular -Other names Radio In The Loop (RITL) Fixed-Radio Access (FRA).

3 Handoff Management and its types. -In a cellular telephone network, handoff is the transition for any given user of signal transmission from one base station to a geographically adjacent base station as the user moves around. -In an ideal cellular telephone network, each end user's telephone set or modem (thesubscriber's hardware) is always within range of a base station. -The region coveredby each base station is known as its cell. -The size and shape of each cell in anetwork depends on the nature of the terrain in the region. -the number of base stations,and the transmit/receive range of each base station. the cells in anetwork overlap; for much of the time, a subscriber's hardware is within range of morethan one base station. The network must decide, from moment to moment, which basestation will handle the signals to and from each and every subscriber's hardware. Intra system handoff inter system handoff. Location Management -maintain seamless connectivity between networks and mobile devices only when we are able to determine the exact current location. -Location Management is implemented in two steps location registration and call delivery or paging -tracking mobiles and locating them prior to establishing incoming calls (deliverying pending messages) -network maintains a location database that needs to be continously updated. Mobile devices send specific signals to the network at dewfinite intervals to inform the network about the divices current location. - it enables the network to keep the databse updated. GPRS GPRS (General Packet Radio Service) is an overlay on top of the GSM physical layer and network entities. Advantages: Short access time to the network for independent short packets ( bytes). No hardware changes to the BTS/BSC Easy to scale Support for voice/data and data only terminals High throughput (up to 21.4 kbps) User friendly billing. It uses exactly the same physical radio channels as GSM, only logical GPRS radio channels are

4 defined. Allocation of the channels is flexible: from one to eight radio interface timeslots can be allocated per TDMA frame. The active users SHARE timeslots, and uplink and downlink are allocated separately. The capacity allocation for GPRS is based on the actual need for packet transfer. GPRS does not require permanently allocated physical channels. GPRS offers permanent connections to the Internet with volume based charging. LEO,MEO,GEO Four different types of satellite orbits can be identified depending on the shape and diameter of the orbit: GEO: geostationary orbit, ca km above earth surface LEO (Low Earth Orbit): ca km MEO (Medium Earth Orbit) or ICO (Intermediate Circular Orbit): ca km HEO (Highly Elliptical Orbit) elliptical orbits LEO Orbit ca km above earth surface visibility of a satellite ca minutes global radio coverage possible latency comparable with terrestrial long distance connections, ca ms MEO Orbit ca km above earth surface comparison with LEO systems: slower moving satellites less satellites needed simpler system design for many connections no hand-over needed higher latency, ca ms higher sending power needed special antennas for small footprints needed

5 GEO Orbit 35,786 km distance to earth surface, orbit in equatorial plane (inclination 0 ) complete rotation exactly one day, satellite is synchronous to earth rotation fix antenna positions, no adjusting necessary satellites typically have a large footprint (up to 34% of earth surface!), therefore difficult to reuse frequencies bad elevations in areas with latitude above 60 due to fixed position above the equator high transmit power needed high latency due to long distance (ca. 275 ms) 5 marks questions Major Components of WLL architecture A.]Wireless Networks Unit(WANU) -contains base station transceivers or Radio Ports(RPs), an Access Manager(AM),Radio Port Control Unit(RPCU) and Home Location Register(HLR). Its main responsibility is to provide authentication,privacy of air interface and managenment of radio resource. -provides operation and maintainance, billing,routing and switching functions. B] Wireless Access Subscriber Unit(WASU) -offers two ait interfaces Uwll and Twll. -Uwll is an air interface toward the network and Twll is a tradional air interface toward subscriber. -This interface facilates services such as protocol conversion and transponding,oam,authentication functions and signalling functions. -provides power supply locally. -Uwll if required can use proprietary protocols or standard air interfaces. Twll can be RJ-11, RJ-45 and so firth. Owll is an air interface that aimed at facilitating OAM to the WLL system. C]Switching Function(SF) -refers to a switch which can be a digital switch that may or may not have advanced Intelligent Network(AIN) capability.

6 Handoff Management and its types What is a Handoff? Handoff refers to a process of transferring an ongoing call or data session from one channel connected to the core network to another. The channel change due to handoff may be through a time slot, frequency band, codeword, or combination of these for time-division multiple access (TDMA), frequency-division multiple access (FDMA), code-division multiple access (CDMA), or a hybrid scheme. Handoff is also called as Handover. Reasons for a Handoff to be conducted: To avoid call termination when the phone is moving away from the area covered by one cell and entering the area covered by another cell. When the capacity for connecting new calls of a given cell is used up. When there is interference in the channels due to the different phones using the same channel in different cells. When the user behaviors change Etc Importance of Handling Handoff: Customer satisfaction is very important in cellular communication and handling handoff is directly related to customer satisfaction. Effective handling of handoff leads to improved reception and fewer dropped calls and results in customer satisfaction which is very important in Mobile communication. Handoff is very common and most frequently occurred in cellular communication so it should be handled efficiently for desired performance of the cellular network. Handoff is very important for managing the different resources in Cellular Systems. Handoffs should not lead to significant interruptions even though resource shortages after a handoff cannot be avoided completely. Thus handling handoffs is very much important for a desired interruption free cellular communication. Design Considerations for handoff: The main goal while designing handoff is to reduce major changes to existing networks esp. at lower levels. This will ensure that existing networks will continue to function as before without requiring current users to change to the new approach. Types of Handoffs:- Handoff is the mechanism which transfers an ongoing call from one cell to another cell as

7 users are near to the coverage area of the neighbouring cell. If handoff does not occur quickly, the Quality of Service (QoS) will degarde below an acceptable level and the connection will be lost. Handoffs are classified into two categories hard and soft handoffs, which are further divided among themselves. Hard handoff: A hard handoff is essentially a break before make connection. Here the link to the prior base station is terminated before or as the user is transferred to the new cell s base station. This means that the mobile is linked to no more than one base station at a given time. A hard handoff occurs when users experience an interruption during the handover process caused by frequency shifting. A hard handoff is perceived by network engineers as event during the call. These are intended to be instantaneous inorder to minimize the disruption of the call. Hard handoff can be further divided as intra and inter-cell handoffs. Intra and inter-cell handoffs: In intra-cell handoff the source and target are one and the same cell and only the used channel is changed during the handoff. The purpose of intra-cell handoff is to change a channel, which may be interfered, or fading with a new clearer or less fading channel. In inter-cell handoff the source and the target are different cells (even if they are on the same cell site). The purpose of the inter-cell handoff is to maintain the call as the subscriber is moving out of the area of the source cell and entering the area of the target cell. Finally, Hard handoff is permitted between members of different softzones, but not between members of the same softzone. This is primarily used in FDMA and TDMA. Soft handoff: Soft handoff is also called as Mobile Directed Handoff as they are directed by the mobile telephones. Soft handoff is the ability to select between the instantaneous received signals from different base stations. Here the channel in the source cell is retained and used for a while in parallel with the channel in the target cell. In this the connection to the target is established before the connection to the source is broken, hence this is called make-before-break. The interval during which the two connections are used in parallel, may be brief or substantial because of this the soft handoff is perceived by the network engineers as state of the call. Soft handoffs can be classified as Multiways and softer handoffs. Multiways and softer handoffs: A soft handoff which involves using connections to more than two cells is a multiways handoff. When a call is in a state of soft handoff the signal of the best of all used channels can be utilized for the call at a given moment or all the signals can be combined to produce a clear signal, this type is called softer handoff. In soft handoffs the chance that the call will be terminated abnormally are lower. Call could only fail if all the channels are interfered or fade at the same time. But this involves the use of several channels in the network to support just a single call. This reduces the number of remaining free channels and there by reducing the capacity of the network. Soft handoff is permitted between members of a particular softzone, but not between members of different softzones.

8 Purpose of HLR and VLR -The Home Location Register (HLR) is the main database of permanent subscriber information for a mobile network. -The HLR is an integral component of CDMA (code division multiple access), TDMA (time division multiple access), and GSM (Global System for Mobile communications) networks. -Maintained by the subscriber's home carrier (or the network operator where the user initiated the call), the HLR contains pertinent user information, including address, account status, and preferences. -The HLR interacts with the Mobile Switching Center (MSC), which is a switch used for call control and processing. -The MSC also serves as a point-of-access to the Public Switched Telephone Network (PSTN - the fixed network). -The third integral element is the Visiting Location Register (VLR), which maintains temporary user information (such as current location) to manage requests from subscribers who are out of the area covered by their home system. The Basic Parameters stored in the HLR in telecom are listed below: Subscriber ID (IMSI and MSISDN) Current Subscriber VLR (Current Location) Supplementary Services Subscriber to (Caller Tone, Missed Call Alert, Any Other Services etc.) Subscriber Status (Registered or Deregistered) Authentication Key and AUC Functionality Mobile Subscriber Roaming Number VLR The VLR contains a copy of most of the data stored at the HLR. It is, however, temporary data which exists for only as long as the subscriber is active in the particular area covered by the VLR. The VLR database will therefore contain some duplicate data as well as more precise data relevant

9 to the subscriber remaining within the VLR coverage (here coverage means status of customer of last lac location area code updation ) The VLR provides a local database for the subscribers wherever they are physically located within a PLMN, this may or may not be the home system. This function eliminates the need for excessive and time-consuming references to the home HLR database. The additional data stored in the VLR in telecom is listed below: Location Area Identity (LAI). Temporary Mobile Subscriber Identity (TMSI). Mobile Station Roaming Number (MSRN). Mobile status (busy/free/no answer etc.). Location Area Identity in Both VLR and HLR in TELECOM Cells within the Public Land Mobile Network (PLMN) are grouped together into geographical areas. Each area is assigned a Location Area Identity (LAI), a location area may typically contain 30 cells. GPRS network Architecture Architecture in GPRS?

10 It uses exactly the same physical radio channels as GSM, only logical GPRS radio channels are defined. Allocation of the channels is flexible: from one to eight radio interface timeslots can be allocated per TDMA frame. The active users SHARE timeslots, and uplink and downlink are allocated separately. The capacity allocation for GPRS is based on the actual need for packet transfer. GPRS does not require permanently allocated physical channels. GPRS offers permanent connections to the Internet with volume based charging. Class A Terminals operate GPRS and other GSM services simultaneously. Class B Terminals can monitor all services, but operate either GPRS or another service, such as GSM, one at a time. Class C Terminals operate only GPRS service. GPRS Network Services Point-to-Multipoint (PTM-M): Multicast service to all subscribers in a given area. Point-to-multipoint (PTM-G): Multicast service to pre-determined group that may be dispersed over a geographic area. Point-to-Point (PTP): Packet data transfer: Connectionless based on IP and CLNS called PTP-CLNS. Connection-oriented based on X.25 (PTP-CONS). Also provides a bearer service for GSM s SMS. GPRS has parameters that specify a QoS based on precedence, a priority of a service in relation to another service (high, normal, and low), reliability and transmission characteristics required. Three reliability cases are defined and four delay classes (end-to-end delay between the mobile terminals and the interface to the network external to GPRS).