TelecomStudy18

1       Larger Capacity : let us discuss this issue with the help of Shannon’s Theorem. It states that the channel capacity is related to product of available band width and S/N ratio. C         = W log 2 (1+S/N) Where C         = channel capacity             W        = Band width available             S/N      = Signal to noise ratio. It is clear that even if we improve S/N to a great extent the advantage that we are expected to get in terms of channel capacity will not be proportionally increased. But instead if we increase the bandwidth (W), we can achieve more channel capacity even at a lower S/N. That forms the basis of CDMA approach, wherein increased channel capacity is obtained by increasing both W & S/N. The ...

Walsh Code : In CDMA the traffic channels are separated by uinique “Walsh” code. All such codes are orthogonal to each other. The individual subscriber can start communication using one of these codes. These codes are traffic channel codes and are used for orthogonal spreading of the information in the entire bandwidth. Orthogonality provides nearly perfect isolation between the multiple signals transmitted by the base station. The basic concept behind creation of the code is as follows: (a)        Repeat the function right (b)        Repeat the function below (c)                 Invert function (diagonally) 0  -----  0          0 --------           0          0   ...

The Wireless Local Loop platform is a versatile supplement or substitute for wired local switching service. Based on IS-95 cdmaOne and 1XRTT, it possesses the quality, reliability and functionality of wired networks with the quick, cost-effective deployment associated with wireless access. It's an exceptionally powerful product for creating revenue. It is connected with mobile stations through air interfaces on one hand, and with Local Exchange(LE) through V5-interfaces on the other. The WLL system enables complete transparency to the Local Exchange (LE) services, such as PSTN call, charging meters, reverse polarity, and variable data services.             WLL consists of the following two primary components that are required to supply telecommunication services to subscribers: 1. BSC: The main controller of the WLL system. The BSC is connected to both the LE and radio base stations and can be located either at the LE bu...

The Call Processing Subsystem (CPS) is the hub for the BSS system’s resource management and call signaling protocol processing. The CPS contains only two modules — call processing module (CPM) and power alarm module (PAM). The CPM is connected to a port of the NIM module in the HIRS through an RS422 interface, and communicates with other subsystems in the BSC (including SVBS, BSM and the NCM module of the HIRS) and the BDS subsystem in the BTS via the HIRS. Since the CPS does not contain many boards, it shares the same frame with the CDSU and GPSTM, as sketched in Fig   Call Processing Module (CPM) CPM is short for Call Processing Module. In the BSC of the CDMA WLL system, the CPM is responsible for call management. As the concentration point of SCWLL system management and signaling processing, its main functions are signaling processing of the Abis interface of the whole CDMA WLL system, wireless resource management and assignment, ground link resource manage...

SVM (Selector & Vocoder Module) is the basis for the SVBS, and each SVM contains 15 vocoders. The SVMs are mainly responsible for the conversion between 64kb/s coding and QCELP coding. They are the center of voice data processing in the BSC. They support voice channels in soft handoff by means of multi-channel backward packet service data selecting function. They take part in backward outer-loop power control by means of backward FER statistics and adjustment of backward SNR threshold. Modularized design is employed on the hardware, and state-of-the-art technologies are adopted on the basis of careful analysis and studies. Product upgrading and development potentials, as well as various factors such as thermal design and electromagnetic compatibility design have been taken into consideration from the selection of components to PCB arrangement, so as to ensure the board reliability. Basic Structure and Functions of SVM The functions of SVM are briefly described as fol...

  NIM is the short form of Net Interface Module, which is the interface unit for the access of various port devices in the SCWLL BSS system to the HIRS network. Based on the current overall design requirement, each HIRS frame of the BSC contains 18 NIM boards, of which 16 are working boards and two are standby boards, forming two N+1 backup systems. The active/standby switchover is implemented in the daisy chain mode. Each NIM board provides eight bi-directional 422 ports, with the supporting data rate being 8Mb/s. In addition, various clocks required for various devices, such as even second and chip signal, are also transmitted in form of differential signals through the 422 port of the NIM boards.      Basic struct ure and Functions of NIM Control unit : Implements board startup, self-test, status error reporting, N+1 switchover etc. DISCO logic : Transmits the data in the reception buffer to the UGATE of the NCM, or saves the data from the UGATE...

The network control module (NCM) is the core module of the HIRS frame. At the same time, as a relatively independent unit, its CPU system is connected downward to an NIM port through an RS422 for the communication with other boards of the system to implement monitoring of the whole system. Its performance directly affects the HIRS and the whole system. For this reason, active/standby configuration is employed for it. In addition, error locating and automatic recovery technologies have been adopted in the design, and various factors such as thermal design and electromagnetic compatibility design have been taken into consideration from the selection of components to PCB arrangement, so as to ensure the stable and reliable working of the module Basic Structure and Functions of NCM U gateway unit : Implements dual-bus mediation and routing between the present frame and outgoing data. ATM interface unit : Implements interconnection of inter-frame data, and provides interfaces ...

HIRS Network Subsystem  CDMA ( HIRS -  High-speed Interconnect Router Subsystem) The system structure of the whole HIRS adopts fast packet switching network based on shared storage (bus type) and hierarchical and modularized structure. A bus type packet switching network is based on two uni-directional buses — CO and DIS buses, which compose the framework of the HIRS network switching platform. The CO bus is contributing bus.  Under the mediation and control of the U gateway of the NCM module, the NIMs send the data frames received from the RS422 port to the CO bus. After the U gateway receives the data frames from the CO bus, it distributes the data according to the data frame’s destination addresses: to the ATM or DIS bus. The DIS bus (Distribution BUS) is the broadcast distribution bus. Data frames from the directions of both the ATM interface and CO bus are sent to the DIS bus in the broadcast distribution mode under the control of the U gateway. All the ...

8.1.1           Descriptions of inter-entity interfaces    Interface between MSC and BSS (A-interface) In fact, it is the interface between MSC and BSC. Adopting 2Mb/s PCM digital link, the standard protocols for this interface include IS-634, IOS2.4, IOS4.0 etc. A-interface is mainly used to transmit the following information: 1. BSS management information, 2. Call processing, and 3. Mobility management information.   Interface between MSC and VLR (B-interface) This interface is an internal interface, without standard definition. Its functions are as follows: VLR is the location and management database for subscribers that have roamed into related MSC area. When the MSC needs the subscriber data of the particular MSC area, the MSC is to inquire the VLR; in the case of mobile station location updating, the MSC will request VLR to store the related information; when the user activates the supplementary se...

Base station subsystem (BSS) Base station subsystem is the general term for the wireless devices and wireless channel control devices that serve one or several cells. Generally, a BSS contains one more base station controllers (BSC) and base transmitter stations (BTS).  Mobile switch center (MSC)    MSC is a functional entity that performs control and switching to the mobile stations within the area that it serves, and an automatic connecting device for the subscriber traffic between the CDMA network and other public networks or other MSCs. MSC is the kernel of the CDMA cellular mobile communication system, and it is different from a wired switch in that an MSC must consider the allocation of the wireless resources and the mobility of subscribers, and at least it must implement the follows processing activities: 1. Location Registration processing; 2. Handoff.     Gateway MSC (GMSC) When a non-CDMA subscriber calls a CDMA subscriber, t...

Parameter Name Parameter Description Default Value Cdma2000CellRelationId The value component of the Relative Distinguished Name (RDN). externalCdma2000CellRef Reference to a ExternalCdma2000Cell. includeInSystemInformation Indicates if the CDMA2000 cell referred to is included in System Information. When the includeInSystemInformation is set to false, the CDMA2000 cell is not  included in SIB8. A maximum of 32 CDMA2000 cells can be included in SIB8. true freqCdma Identifies the carrier frequency within a CDMA2000 Band. Cdma2000FreqId The value component of the Relative Distinguished Name (RDN). reservedBy Contains a list of MO instances that reserve this MO instance. Cdma2000FreqBandId The value component of the Relative Distinguished Name (RDN). ...