TelecomStudy18

Main differences between the third and second generation air interfaces are described. GSM and IS-95 (the standard for cdmaOne systems) are the second generation air interfaces considered here. Other second generation air interfaces are PDC in Japan and US-TDMA mainly in the Americas; these are based on TDMA (time division multiple access) and have more similarities with GSM than with IS-95. The second generation systems were built mainly to provide speech services in macro cells. To understand the background to the differences between second and third generation systems, we need to look at the new requirements of the third generation systems which are listed below:        ·          Bit rates up to 2 Mbps; ·          Variable bit rate to offer bandwidth on demand; ·          Multiplexing of services with different quality requir...

In the late 1980s, the groups involved in developing the GSM standard realized that within the given time-frame they could not complete the specifications for the entire range of GSM services and features as originally planned. Because of this, it was decided that GSM would be released in phases with phase 1 consisting of a limited set of services and features. Each new phase builds on the services offered by existing phases. Phase 1 Phase 1 contains the most common services including: ·          Voice telephony ·          International roaming ·          Basic fax/data services (up to 9.6 kbits/s) ·          Call forwarding ·          Call barring ·          Short Message Service (SMS) Phase 1 also incorporated features such...

The features Remote OMT (Operation and Maintenance Terminal) and Remote OMT over IP are updated to support the new RBS 6000 DUG-20/RUS-01 configurations. In MCPA backwards compatible mode, having a BTS G11A or newer in a BSS 07B-G10B network, the configuration of an MCPA is made using OMT. Configuration in MCPA single mode (BTS G11B with BSS G10B or newer) is made from the BSC, refer to Section 5.7 on page 43. All TRXs in a DUG are connected to one or several RUSs. It is the connections between RUSs and antennas that will decide which MCPAs to use for which antenna sectors (cells). Each antenna sector is configured in the OMT with the default configuration of 3*20W (3*43.0 dBm) per MCPA. If desired it is possible to choose a different number of TRXs per MCPA, and it is possible to choose some configurations where the total MCPA mean power will end up on less than 60 W (47.8 dBm). Also the levels 40W (46.0 dBm) and 20W (43.0 dBm) are available. The chosen number of TRXs...

Automatic FLP will enable operators to run Frequency Load Planning (FLP) networks, including Synchronized Radio Networks, with minimum effort and maximum performance. The feature performs daily downlink interference matrix measurements and creates synchronization clusters for synchronization status monitoring. FLP parameters are continuously supervised and automatically adjusted to network changes when needed due to for instance lost synchronization, addition of TRX HW, or changes in hopping frequency sets. The parameters that are put under direct BSC control by Automatic FLP activation are, HSN, FNOFFSET, MAIOs, TSC and FSOFFSET. By using Automatic FLP an operator will get the following benefits: ·           Maximum capacity gain from FLP (best parameter configuration always used. Parameter settings can be kept continuously optimized) ·          Maximizes performance in all types of FLP networks (for example low...

  Broadcasts LTE system information in the GSM network to enable idle and packet transfer  mode cell reselection from GSM to LTE networks. Each GSM cell broadcasts information about: • Neighboring cells (WCDMA and LTE) • Thresholds for IRAT • Priority between GSM, WCDMA and LTE cells The information is broadcasted in the GSM network via the system information message SI2quater. The main purpose with priority based cell reselection is to allow reselection to LTE, but at the same time it also introduces cell reselection based on priority towards WCDMA. This is an alternative to the existing non priority based cell reselection to WCDMA. When cell reselection to LTE is used, cell reselection to WCDMA will be priority based as well. In MSs not supporting priority based cell reselection, the non-priority based cell reselection to WCDMA is used if the feature "GSM-UMTS Cell Reselection and Handover" is activated. Commands and Printouts • RLSRI: Radio Contro...

 GSM uses Time Division Multiple Access (TDMA) as its access scheme. This is how the MS interfaces with the network. TDMA is the protocol used on the Air (Um) Link. GSM uses Gaussian Minimum-Shift Keying (GMSK) as its modulation methods. Time Division means that the frequency is divided up into blocks of time and only certain logical channels are transmitted at certain times. Logical channels will be introduced in the next lesson. The time divisions in TDMA are known as Time Slots. Time Slots : A frequency is divided up into 8 time slots, numbered 0 to 7.

The ARFCN is a number that describes a pair of frequencies, one uplink and one downlink. The uplink and downlink frequencies each have a bandwidth of 200 kHz. The uplink and downlink have a specific offset that varies for each band. The offset is the frequency separation of the uplink from the downlink. Every time the ARFCN increases, the uplink will increase by 200 khz and the downlink also increases by 200 khz. The given below table summarizes the frequency ranges, offsets, and ARFCNs for several popular bands. Calculating Uplink/Downlink Frequencies The following is a way to calculate the uplink and downlink frequencies for some of the bands, given the band, the ARFCN, and the offset. GSM 900 Uplink = 890.0 + (ARFCN * .2) & Downlink = Up + 45.0 Example:  Given the ARFCN 72, and we know the offset is 45MHz for the GSM900 band: Up = 890.0 + (72 * .2) Up = 890.0 + (14.4) Up = 904.40 MHz Down = Up + Offset Down = 904.40 + 45.0 Down = 949.40 MHz ...

Its main role is to manage the communications between the mobile users and other users, such as mobile users, ISDN users, fixed telephony users, etc. It also includes data bases needed in order to store information about the subscribers and to manage their mobility. The different components of the NSS are described below.   The Mobile services Switching Center (MSC) It is the central component of the NSS. The MSC performs the switching functions of the network. It also provides connection to other networks.    The Gateway Mobile services Switching Center (GMSC) A gateway is a node interconnecting two networks. The GMSC is the interface between the mobile cellular network and the PSTN. It is in charge of routing calls from the fixed network towards a GSM user. The GMSC is often implemented in the same machines as the MSC. Home Location Register (HLR) The HLR is considered as a very important database that stores information of the subscribers belonging to the...

Interleaving is a simple, but powerful, method of reducing the effects of burst errors and recovering bits when burst errors occur. The symbols (output of Forward Error Correction Coder) from each group are interleaved in a pattern that the receiver knows. The interleaver is located at the BTS and in the phone.

Duplexing : Duplexing is the technique by which the send and receive paths are separated over the medium, since transmission entities (modulator, amplifiers, demodulators) are involved. There are two types of duplexing.\ 1. Frequency Division Duplexing FDD 2. Time Division Duplexing TDD        Frequency Division Duplexing FDD Different Frequencies are used for send and receive paths and hence there will be a forward band and reverse band. Duplexer is needed if simultaneous transmission (send) and reception (receive) methodology is adopted .Frequency separation between forward band and reverse band is constant Time Division Duplexing (TDD) TDD uses different time slots for transmission and reception paths. Single radio frequency can be used in both the directions instead of two as in FDD. No duplexer is required. Only a fast switching synthesizer, RF filter path and fast antenna switch are needed. It increases the battery life of mobile phon...

–The purpose of the Cell Load Sharing feature is to distribute some of a cells traffic load to surrounding cells during peaks in traffic. −This is achieved by moving established connections to neighboring cells that have idle resources. −Cell Load Sharing increases the number of handovers in the part of the network where the traffic load is unevenly distributed -Cell Load Sharing is activated on the BSC level via parameter LSSTATE (Active/Inactive) and activated on cell level via parameter CLSSTATE (Active/Inactive) –The traffic load (amount of idle full rate TCHs) on each cell is examined by the BSC every CLS time Interval defined by a parameter CLSTIMEINTERVAL (default=100msec) −If the percentage of idle full rate traffic channels is ≤ parameter CLSLEVEL, then this cell will try to get rid of some traffic by initiating cell load sharing handovers to neighbors. −For a neighbor cell to accept HOs due to cell load sharing then parameter HOCLSACC should be set to ...

Multi Band Cells (MBC) A multi band network consists of cells from different frequency bands for example: 900/1800 MHz −By combining these frequencies in the same cell with 1 common BCCH, the radio performance and traffic capacity are improved where the no. of cells and -Using MBC concept with only 1 BCCH, this will reduce the no. of defined neighbors to 50% leading to better accuracy for the measurement reports coz there will be more time available for measurements for each neighbor. -The Dynamic OL/UL subcells (Concentric cells) is a prerequisite feature for the Multi Band Cells. −Mostly the frequency band with “Better coverage” (i.e. lower frequency band) is configured as the Underlaid subcell while the other frequency band with “Worse coverage” (i.e. higher frequency band) is configured as the Overlaid Subcell. −Ex: 900MHz frequency band UL, while 1800MHz frequency band OL −It is recommended to select the BCCH frequency to lie in the “Better Covera...

−Traffic Capacity of a cellular network can be increased by either adding more frequencies or reducing the frequency reuse distance. −One approach is to apply a second frequency re-use pattern with a tighter frequency reuse (Overlay) on the existing pattern. −These cells should be restricted in size, so shorter reuse distance can be accomplished without causing Co-channel/Adjacent channel interference. −They are termed Overlaid (OL) Subcells, whereas the original cells will be called Underlaid (UL) Subcells. −Now by having more frequencies per cell, then Network capacity is increased -The fundamental idea behind the OL/UL subcells is to let the traffic close to the site to be moved to the OL subcell, while traffic close to the cell border to be moved to the UL subcell. −In that way of treading the traffic, the frequencies in the OL subcell can have tighter frequency reuse. -Using the OL/UL concept we can solve the case as follows: -f4 will be used in the...

Paging Groups −The MS will monitor the incoming paging in only specific times, and the rest of the time it will remain in sleeping mode. −In this way we save the MS battery and we decrease the UL interference on the system. −The MS will monitor the incoming paging when the “Paging Group” assigned for this MS is transmitted only. −The CCCH block can be used by either PCH or AGCH. −When the CCCH block is used for paging it will be called “Paging Block” −The Paging Block consists of 4 consecutive Time slots lie in 4 consecutive frames. −The Paging Block can be used to page 4/3/2 users according to IMSI or TMSI is used when paging the MS ( Length IMSI = 2 TS, Length TMSI = 1 TS) −The group of users belong to the same paging block will be called “Paging Group” 

MCC  MNC  MSIN ( 3Digits) ( 2Digits) ( 10Digits) IMSI : International Mobile Subscriber Identity  IMSI = MCC + MNC + MSIN MCC= Mobile Country Code (3 digits) MNC= Mobile Network Code (2 digit ) MSIN= Mobile Subscriber Identification Number (10 digits) Ex: IMSI = MCC-MNC-MSIN = 404-22-1234567890 where, 602 -  India Country Code 22  -   Bharti Airtel  Network Code 1234567890 -  Mobile Subscriber Identification Number MSISDN : Mobile Station Integrated Services Digital Network MSISDN = CC + NDC + SN CC= Country Code (2-3 digits) NDC= Network Destination Code (2-3 digit ) SN= Subscriber Number ( max 10 digits)

KPIs to be monitored: ·             SD Blocking ·             SD Drop SDCCH Channel: ·    SDCCH channel is a dedicated channel which is using for LAC updation, Call Setup, SMS in Ideal mode. It works in UL & DL SD Blocking: ·    SD Blocking means that you are not getting SD resource for the call origination. When MS connects with Network then RACH and AGCH are provided. After AGCH, SDCCH is provided but if SDCCH is not provided at this time due to some problem or due to unavailable of SD by BSC. KPI Formula in Ericsson: ·             SDCCH CONGESTION = (CCONGS / CCALLS) * 100 ·             CCONGS - Congestion counter. ·  ...