Method and arrangement for satisfying performance requirements by tuning parameters for accessing a network with random access channels

A method for satisfying random access attempt success requirements of a random access channel (RACH)used by a mobile station (MS) for accessing a communication network accessible in a communication cell served by a radio base station (BS), said mobile station(MS) communicating on uplink and downlink channels,

• the method comprising the steps of:
• gathering data during a time period, the data including a number of preamble transmission attempts to the base station made by the mobile station in order to perform a successfully executed ramdom access to the base station,
• estimating quantities related to random access attempt success statistics in said cell based on the gathered data, and
• tuning random access parameters such that said estimated quantities related to random access attempt success statistics statisfy predetermined random access attempt success requirements,
• wherein said tuning of random access parameters includes the steps of:
• using reports from the MS about the number of preamble transmission attempts and knowledge of a current MS transmit power ramping step to adjust received power estimates for the MS to a corresponding received power for a first random access attempt,
• gathering data from all random accesses during a certain time to compile an estimate of a distribution of the received power for a first random access attempt,
• using a detection threshold level level of a desired target receive random access power, a detection miss probability after one transmission attempt, and a cumulative distribution of the received power first random access attempt to determine a new level of said desired target receive random access power.

A communication network node for enabling tuning of a random access channel used by a mobile station (MS) when requesting access to a communication network system in a communication cell served by a radio base station (BS), the mobile station and base station communicating on uplink and downlink channels, the communication network node comprising:

• a storage unit configured to gather data during a time period, the data including a number of preamble transmission attempts to the base station made by the mobile station in order to perform a successfully executed random access to the base station, and
• a Random Access (RA)optimizing processor, connected to the storage unit, configured to:
• estimate quantities, including a false detection probability, related to random access attempt success statistics in said cell based on the gathered data, and
• tune random access parameters such that said estimated quantities related to random access attempt success statistics satisfy predetermined requirements, and
• use said false detection probability and requirements on a maximum false detection probabiiity to compute a detection threshold.