Alex_R
2011-06-22, 08:59 PM
Dynamic PBT is timeslot-based. Normally, two TRXs in a double-transceiver unit work independently. If required, the two channels of the same timeslot number on the two TRXs work as a channel group. That is, the two channels can be converted into a channel group, and the channel group into two independent channels. This balances cost, capacity, and coverage. Dynamic PBT increases resource utilization and assists in expanding the coverage.
Note
When the double-transceiver unit works in dynamic PBT mode, the channels with the same timeslot number on the two TRXs of the same double-transceiver unit form a PBTchannel group. The two channels must be TCHs (TCHF or TCHH). The channel with a smaller TRX number is the primary channel, and the other channel is the secondary channel. The primary channel and the secondary channel are the channels with the same timeslot number on one double-transceiver unit.
BCCHs, SDCCHs, PDCHs, and CBCHs cannot form a channel group. They can only be used as independent channels.
During channel assignment, the BSC searches for the optimal channels. After dynamic PBT is enabled, the BSC determines whether the optimal channels can form a PBT channel group if the PBT channel group should be assigned. If a PBT channel group can be formed, the BSC blocks the secondary channel. Then, the BSC assigns the channel group to the call. If the optimal channels cannot form a channel group, the BSC regards the channels as independent channels. If the optimal channels can form a channel group but one of them is occupied by a call, the BSC attempts to hand over the call to another channel. After the channel turns idle, a channel group is formed and then assigned to the call.
In dynamic PBT mode, the downlink-limited handover decision algorithm is added to determine whether the downlink signal strength is limited. If the downlink signal strength is limited and the serving cell supports dynamic PBT, the call is handed over to an available channel group. If one of the two channels with the same timeslot number on one double-transceiver unit is occupied by the call, the call on the other channel should be handed over to another idle channel.
When the downlink signal strength is increased to a certain level, the PBT channel group is not required. The BSC divides the channel group into two independent channels and maintains the call on the primary channel. At the same time, the BSC releases the secondary channel to increase the capacity of the cell.
Note
After dynamic PBT is enabled, the BSC reserves most possible channel pairs that can form channel groups during the assignment of normal independent channels.
With dynamic PBT used in the overlaid subcell, the coverage of the overlaid subcell is expanded through the handover of calls in the vicinity of the edge to the overlaid subcell. This helps to balance the traffic in the overlaid subcell and that in the underlaid subcell and also increase the success rate of handover from the underlaid subcell to the overlaid subcell.
Dynamic PBT is a software solution. That is, the hardware connections of the BTS in dynamic PBT are the same as those in PBT, and only the software needs to be upgraded.
Note
When the double-transceiver unit works in dynamic PBT mode, the channels with the same timeslot number on the two TRXs of the same double-transceiver unit form a PBTchannel group. The two channels must be TCHs (TCHF or TCHH). The channel with a smaller TRX number is the primary channel, and the other channel is the secondary channel. The primary channel and the secondary channel are the channels with the same timeslot number on one double-transceiver unit.
BCCHs, SDCCHs, PDCHs, and CBCHs cannot form a channel group. They can only be used as independent channels.
During channel assignment, the BSC searches for the optimal channels. After dynamic PBT is enabled, the BSC determines whether the optimal channels can form a PBT channel group if the PBT channel group should be assigned. If a PBT channel group can be formed, the BSC blocks the secondary channel. Then, the BSC assigns the channel group to the call. If the optimal channels cannot form a channel group, the BSC regards the channels as independent channels. If the optimal channels can form a channel group but one of them is occupied by a call, the BSC attempts to hand over the call to another channel. After the channel turns idle, a channel group is formed and then assigned to the call.
In dynamic PBT mode, the downlink-limited handover decision algorithm is added to determine whether the downlink signal strength is limited. If the downlink signal strength is limited and the serving cell supports dynamic PBT, the call is handed over to an available channel group. If one of the two channels with the same timeslot number on one double-transceiver unit is occupied by the call, the call on the other channel should be handed over to another idle channel.
When the downlink signal strength is increased to a certain level, the PBT channel group is not required. The BSC divides the channel group into two independent channels and maintains the call on the primary channel. At the same time, the BSC releases the secondary channel to increase the capacity of the cell.
Note
After dynamic PBT is enabled, the BSC reserves most possible channel pairs that can form channel groups during the assignment of normal independent channels.
With dynamic PBT used in the overlaid subcell, the coverage of the overlaid subcell is expanded through the handover of calls in the vicinity of the edge to the overlaid subcell. This helps to balance the traffic in the overlaid subcell and that in the underlaid subcell and also increase the success rate of handover from the underlaid subcell to the overlaid subcell.
Dynamic PBT is a software solution. That is, the hardware connections of the BTS in dynamic PBT are the same as those in PBT, and only the software needs to be upgraded.