03-08-2012, 02:27 PM
Telecommunications MSc in Software Development
[attachment=30049]
GSM Handover
• Handover is the process of switching a radio
connection from one BS to another in order to
maintain seamless radio connection during mobile
station movement
• Handover in GSM is implemented as Mobile Assisted
Handover (MAHO) and backward handover signalling
• GSM handover is hard handover as the old radio link
is released before the new radio link has been fully
established
® due to non-synchronised BTSs
Handover Process
• The handover process in GSM consists of the
following four steps
1. Measurements
2. Handover request
3. Handover decision
4. Handover execution
Handover Criteria
• Permanent data such as transmitter power of
– MS, BTS in supplying cell, BTSs in neighbour cells
• Results of real-time measurements by MS
– downlink signal quality (gross bit-error-rate) - RXQUAL
– downlink receive signal levelof current channel - RXLEV
– downlink receive signal levelfrom neighbour cells
(BCCHs)
• Results of real-time measurements by BTS
– uplink signal quality (gross bit-error-rate) - RXQUAL
– uplink receive signal levelof current channel - RXLEV
– uplink receive signal level from neighbour cells
• Traffic-oriented aspects (cell capacity, no. of free
channels, no. of new connections waiting for TCH)
Measurement Protocol
• Measurements on current radio channel
– measurement of signal strength and link quality of slot in
every frame (4.615ms measurement interval) ® 100 samples
per reporting period of 480ms
– reporting of average values once or twice per second (one or
two 480ms SACCH blocks
• Measurement of channels in neighbour cells
– up to six neighbour cells are considered
– between UL and DL MS has about 2.3ms interval for
measurement of signal level from neighbour cells and 6.9ms
interval to scan for neighbour cell’s BCCH frequency
– MS can measure up to 100 signal level samples per 480ms
divided between the 6 strongest neighbour cells
[attachment=30049]
GSM Handover
• Handover is the process of switching a radio
connection from one BS to another in order to
maintain seamless radio connection during mobile
station movement
• Handover in GSM is implemented as Mobile Assisted
Handover (MAHO) and backward handover signalling
• GSM handover is hard handover as the old radio link
is released before the new radio link has been fully
established
® due to non-synchronised BTSs
Handover Process
• The handover process in GSM consists of the
following four steps
1. Measurements
2. Handover request
3. Handover decision
4. Handover execution
Handover Criteria
• Permanent data such as transmitter power of
– MS, BTS in supplying cell, BTSs in neighbour cells
• Results of real-time measurements by MS
– downlink signal quality (gross bit-error-rate) - RXQUAL
– downlink receive signal levelof current channel - RXLEV
– downlink receive signal levelfrom neighbour cells
(BCCHs)
• Results of real-time measurements by BTS
– uplink signal quality (gross bit-error-rate) - RXQUAL
– uplink receive signal levelof current channel - RXLEV
– uplink receive signal level from neighbour cells
• Traffic-oriented aspects (cell capacity, no. of free
channels, no. of new connections waiting for TCH)
Measurement Protocol
• Measurements on current radio channel
– measurement of signal strength and link quality of slot in
every frame (4.615ms measurement interval) ® 100 samples
per reporting period of 480ms
– reporting of average values once or twice per second (one or
two 480ms SACCH blocks
• Measurement of channels in neighbour cells
– up to six neighbour cells are considered
– between UL and DL MS has about 2.3ms interval for
measurement of signal level from neighbour cells and 6.9ms
interval to scan for neighbour cell’s BCCH frequency
– MS can measure up to 100 signal level samples per 480ms
divided between the 6 strongest neighbour cells