FREQUENCY HOPPING

FREQUENCY HOPPING:- Changing of frequency according to some algorithm in dedicated mode is called frequency hopping.

• In one sec 1/256 times frequency hopping happens.
• Multi wave propagation varies the signal strength which causes fading dips. This is known as Rayleigh fading which is frequency dependent.
• Frequency hopping changes the frequency with time to eliminated frequency dependent Rayleigh fading.
• Frequency hopping reduces the effects of interference and gives a great support to cater the capacity upgrading as well as.

TO USE OF FREQUENCY HOPPING:- To maximize network capacity and minimize the interference and improve the network quality.

There are two types of frequency hopping.
Base band hopping(BBH)

• In this types of hopping, only frequencies used by the TRXs can be allocated to the frequency hopping sequences.
• The BCCH supporting time slots cannot hop. TS0 of the BCCH TRX is always transmitting on the BCCH frequency, other timeslots can use other frequencies unless the BCCH frequency is transmitted by any other TRX at the same time.
• The major advantage of the BBH is the time TS1 to TS7  of the BCCH frequency containing TRX is allowed to perform hopping. But frequency hopping performs best with at least 4 TRx and it is the disadvantage of this system.

Synthesized frequency hopping(SFH)

• In synthesized frequency hopping each frame unit is connected to one carrier unit.
• Hopping is performed by changing the carrier unit by changing a synthesizer.
• As the communication is not hopping between the carrier units but the carrier unit frequency itself is hopping . so many frequencies can be used as hopping frequencies.
• In SFH , TRX returns in every time slot to a different frequency. Thus TCH remains on the same TRX  but the frequencies of that TCH hops.
• In GSM basically used synthesized frequency hopping.

TESTING OF NETWORK

SCFT(Single Cell Function Test)

DRIVE TEST:- Testing the network in particular area to give the real picture of the network's performance on the field with a certain tools.

There are different parts of drive test.

1. Planning
2. Implementation
3. Optimization

Optimization;- It is the process to maximize the network capacity and minimize the interference to improve the network quality.

Dedicated /Continues /Long call Mode:- Making continues call along drive test activity before starting the route , call the drive test no (ex. 199 for X operator) and only stop the call when the route finish.

* To see the quality and coverage of the network.

Ideal mode:- Along the drive test activity the MS is "ON" but no call occur. 

TEMS:-Test mobile system product by ERKSSON solution.This tools  developed for wireless network to plan/ optimize and expand their system. A test tool use to read and control information sent over the air interface between the base station and the mobile station in GSM or cellular system . It can also used for radio coverage measurement.

GSM : GLOBAL SYSTEM FOR MOBILE COMMUNICATION

  GSM

         It is a set of recommendations and specification for a digital cellular telephone network.

         A GSM Network comprises of many function units.

• MOBILE STATION:- The Mobile station consists of physical equipment such as SIM card, Display and digital signal processor, Radio transceiver.It provides.

              1. Teleservices

              2. Data bearer services

              3. Air interface to the user

              4. The features' supplementary services

The MS also provides receptor for SMS messages, enabling the user to toggle between voice and user data.The mobile system facilitates access to voice messaging system. The MS also provides access to the various data service available in a GSM network.

* GSM system provides a greater subscriber capacity than analogue system, 

* GSM system allows 25KHz per user

SIM

 SIM(SUBSCRIBER IDENTIFICATION MODULE) :- By making a distinction between the subscriber identity and the mobile equipment identity, a GSM PLMN can route calls and perform billing based on the identity of the subscriber rather than the mobile equipment being used. This can be done using a removable Subscriber Information Module (SIM). A ”smart card” is one possible implementation of a SIM module

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MSISDN:-MSISDN means "mobile subscriber integrated services digital network". It is the telephone no of the MS. This is the no a calling party dials to reach the subscriber.It is used by the land network to route calls towards the MSC.

              MSISDN= CC+NDC+SN

CC-Country code (e.g for india , country code is 91)

NDC-National destination code

SN-Subscriber number

IMSI:- IMSI means "International mobile subscriber identity". It is a no that network identify unique to a SIM.It is the primary identity of the permenantly assigned to that subscriber.

               IMSI=MCC+MNC+MSIN

MCC-Mobile country code  (e.g for india, mobile country code is 404)

MNC-Mobile network code (it is a two digital code)

MSIN-Mobile subscriber identity number ( it is a ten digital code)

IMEI:- IMEI means "International mobile equipment identity".It is serial number unique to each mobile.This no  is permanently stored in the mobile equipment.IMEI can be used to identify MS, that are reported stolen or operating incorrectly.

           IMEI=TAC+FAC+SNR+SP

TAC-Type approval code (it is six digit code)

FAC-Final assembly code(it is two digit code)

SNR- Serial no( it is six digit code)

SP-   Spare( it is single digit code)

TMSI:-The GSM system can also assign a Temporary Mobile Subscriber Identity (TMSI). After the subscriber’s IMSI has been initialized on the system, the TMSI can be used for sending backward and forward across the network to identify the subscriber. The system automatically changes the TMSI at regular intervals, thus protecting the subscriber from being identified by someone attempting to monitor the radio channels. The TMSI is a local number and is always transmitted with the Local numbers and is always transmitted with the Location Area Identification (LAI) to avoid ambiguities.

EIR:- EIR means" Equipment identity register". A listing of the allowed IMEI is maintained by the PLMN’s in the Equipment Identity Register (EIR) to validate the mobile equipment.