Handoff parameters AJAL.A.J Assistant Professor –Dept of ECE,Federal Institute of Science And Technology (FISAT) TM MAIL: email@example.com
Handoff parameters• Word error indicator ( WEI )• Received signal strength indication (RSSI)• quality Indicator (QI)
Word error indicator ( WEI )• This is a measure to check the output of the demodulator in the receiver.• When the carrier input to the demodulator is sufficient above the threshold , the output will be with less WEI
Received signal strength indication (RSSI)• The Received signal strength must be around - 100 dBm
quality Indicator (QI)• This is a measure of the signal quality with respect to interference.• Usually it is prescribed at 5 dB to 25 dB
Types of handoff• The handoff can be classified into 3 categories depending upon the strategies involved in the handoff detection they are :1.Mobile controlled handoff (MCHO)2.Network controlled handoff (NCHO)3.Mobile assisted handoff (MAHO)
1.Mobile controlled handoff (MCHO)• This is a handoff technique introduced by DECT and north American PACES.• In this strategy the mobile station in real time checks the qualities of reception.• When the qualities go below a prescribed value, it will handoff the neighbouring cell channel carriers for required quality.• the mobile unit informs the MSC about a suitable channel through which quality transmission could be achieved.• The handoff will be carried out as soon as it gets that channel allotted to it.
2.Network controlled handoff (NCHO)• This technique is followed by CTZ and AMPS .• Here the responsibility of channel quality measurement is left with base station.• In real time the BS measures WEI and RSSI .• When these parameters go below the quality mostly the BS initiates handoff through MSC.• The MSC will allocate a free channel in the incumbent call by suitable testing.
Testing!• The procedure for testing the channel for its freeness depends on the modulation and the multiplexing techniques adopted in the system.• This kind of handoff will take relatively more time to complete the function.
Processing time !• This kind of handoff will take relatively more time to complete the function.• The measured values of the quality parameter has to come from the BS’s for a final decision