CherriesWorkPersonal Views, Wireless Optimization, Leadership and Management

Optimizing Maximum Cell Power in Multi-Carrier3G/HSPA+ Networks

3G networks are witnessing tremendous increase in traffic especially data trafficon HSPA service. This increase in HSPA traffic affected negatively the Signal toNoise Ratio of the whole cell and degraded voice call performance in terms ofcall quality, accessibility and retain-ability. This drives many operators to deploymultiple carrier in the same sector in order to accommodate for the data trafficincrease, and protect voice quality. One important challenge an operator face isto allocate the power among the carrier in order to maintain minimum powerutilization, maximize cell throughput, and minimize congestion in the networkdue to scarcity of power resources.I developed an optimization model that I used in practical networks to optimallyset maximum transmit power of the cell carrier such that the power utilization isminimized on the whole sector, and it’s balanced between the cell carriers.Let me first define some quantities:

is the maximum power amplifier power of a sector.

are the current maximum average power used in cell n of a sector.Where n is the number of carriers deployed in the network.

are the maximum cell power used in cell 1 and 2 of a sectorrespectively. These are the quantities that we need to optimize.

We can then model the power utilization minimization problem as

The objective function ensures a balanced power utilization between the carriersaccording to the load situation. This objective function is a convex optimizationproblem that can be solved in polynomial time. The first conditions restricts thetotal transmit power of the whole sector to be the maximum power of the

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April 27, 2012 Leave a reply

power amplifier. Finally, the last condition ensures that the transmit power of acell shall never exceed the power amplifier power and shall never drops below

which is a design parameter. In the special case of two carriers, the solution canbe simplified to a much simpler and straight forward formulation.

Results from live networks deploying two carriers by applying this algorithm areexcellent. I managed to improve throughput by 20%, reduce power utilizationand hence congestion. It worth mentioning also that the improvement inthroughput is not restricted to highly utilized cells but also to low utilized one.The Chart below is showing how power utilization varies on first and secondcarrier cells by tuning the maximum transmit power of the first carrier. The redvertical line demonstrates the typical current maximum transmit power settingin the network, while the green vertical line is showing the optimal settings.

Power Utilization improved from 80% to 55% On Second Carrier Cell.In the example scenario shown PA Power = 60W.

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