GSM - TRX Planning

ZTE Magic RRU consists of 6 ports to which 3 PA (power amplifiers) can be connected. Each PA supports 80 Watt linked with a sector/cell and the power is distributed uniformly among the TRXs connected to a PA. This means that with a minimum recommended power of 20 W per TRX, no more than 4 TRXs should be configured on one PA or sector. Thus, for a site having 3 sectors, 444 configuration is suitable.

Transmission requirement for TRX depends on multiple factors such as:

• TRX configuration
• Coding Scheme - Higher coding scheme (MCS-9) requires more transmission bandwidth
• Number of static and dynamic PDCH configuration
• Half Rate utilization

In general, a site with a 444 configuration, 2 static and 4 dynamic PDCHs per cell, 100% Half Rate utilization, and an average of MCS6 can be supported by 1 E1 (2.048 Mbps).

GSM - TCH Availablility

TCH Availability is the ratio available TCH (Full Rate, Half Rate, dynamic radio channels) to the total available and unavailable TCH (Full Rate, Half Rate, dynamic radio channels). Generally, TCHA follows the pattern of available TCH/F and dynamic radio channel.

TCHA is one of the first KPI that should be checked in environments where power outages are common. It degrades blocking, DCR, HOSR and other KPIs to a large extent. More often than not, low TCHA of neighboring cell causing severe KPI degradation in a particular cell. It is always safe to revive TCHA of the network before implementation of parametric or design changes for KPI improvement.

Major alarms causing low TCHA are STP link association broken (transmission), and GENSET on (power outage).

UMTS - Types of congestion

UMTS cells can have below congestion types:

1. CE (Channel Elements) Congestion:  This happens when resources on the hardware are fully utilized. One solution is to add extra cards/boards in the Node B to increase capacity. For example, ZTE has BPK1 and BPKd cards that comprises of 384 and 768 CE respectively. CE congestion is always monitored by observing UL CE (since UL CE consumption is always greater than that in the DL)
2. Code Congestion:  High number of users could result in code congestion. Parameters such as minHSDPA users can be decreased to make room for cell DCH users. Carrier expansion can be done to accommodate larger  number of users.
3. TCP Congestion:  This represents that Total Carrier Power limit has been reached. Addition of Power Amplifier, new nodes/sites, decreasing CPICH power, or increasing cell transmission power are some of the remedial steps for rectification. 
4. Iub Congestion:  Congestion results due to fully utilized transmission media which can be increased to resolve the issue.