Origination Message Tx from MS or General Page Tx from BS Origination Message Rx at BS or Page Response Rx at BS Admission Blocked CallAccess Failure Channel Assignment Message Tx from BS Connection Setup Failure Service Connect Complete Message Rx at BS Service Dropped Call Call Connectivity Lost Performance Management Terminology (cont.)
Handoff process When a MS is moving from one cell to another, the MS undergoes procedures, called handoff, that allow the MS to acquire the pilot channel transmitted by neighboring BTS and to make another connection to a new BTS, while maintaining a connection to the old base station transceiver system (BTS).To perform a handoff process, every MS measures and internally stores the information about neighboring Forward Pilot Channels (FPiChs) acquired in its current location.
Handoff Pilot Sets Active set Pilots of CDMA carriers whose forward paging channels of Forward Common Control Channels (FCCChs) are being monitored while in idle state. During a call, these are the pilots associated with forward traffic channels assigned to the MS. Candidate set Pilots not currently in the active set but with enough signal power level to become an active pilot. Neighbor setPilots that do not belong to the active or candidate sets but may also be considered candidates for a handoff process Remaining setAll remaining pilots that do not belong to any of the other sets but are in the area where the MS is located;
Handoff Types Soft handoffA soft handoff is applied to an MS that starts communication with a new BTS while still connected to another BTS Make-before-break Hard handoff A MS is disconnected from one BTS and is switched to another Break-before-make Softer handoff A special soft handoff between sectors in the same BTS Idle handoffAn idle handoff is performed while in idle state when the MS is moving from one BTS to another Access handoffAn access handoff occurs in the system access state when the MS is performing access attempts.
Power Control FER is the most common network quality parameter to execute power control Ec/Io (ratio of chip energy, Ec, to interference plus noise spectral density) Eb/Io (ratio of bit energy, Eb, to interference plus noise spectral density)Power control aims to quickly and efficiently estimate the minimum MS transmission power to achieve the required communication quality (based on FER statistics) Benefits of power control in CDMA systems Increase in system capacity Minimization of near-far effect Increase in battery lifetime
Open loop power controlUsually implemented as the initial power control to give an estimate of minimum transmission power used for access channels, such as Reverse Access Channels (RAChs), Enhanced Access Channels (EAChs), and Reverse Common Control Channels (RCCChs), during system access state. Closed loop power controlUsually implemented for traffic channels, which need a more sophisticated power control system. cdma2000 systems can also employ this type of power control even during the system access state.
Procedure of the closed loop power controlA) An MS initially uses the transmission power defined in the last message from last access probe transmitted on the system access state. B) The BTS determines a ‘set point’ power level, which is considered ideal for receiving signals within a certain QoS. C)The set point is periodically adjusted. D) The BTS performs power control by transmitting power control bits, whichinstruct MSs individually to increase or reduce transmission power according to the estimated set point value.