Mobile telecommunication systems can offer high bit rate services. The demand is increasing and believed to increase even further in the future. To meet the demand and at the same time build systems that are justified from an economic perspective, and from the perspective of usage of limited resources such as radio bandwidth, is a challenge. In the area of radio resources several techniques are in use, or proposed, to achieve an efficient radio resource management (RRM). The description of prior art and also the invention will have a starting point in the present mobile communication system referred to as UTRAN. UTRAN stands for UMTS Terrestrial Radio Access Network, and UMTS for Universal Mobile Telecommunication Communication System. The references to UTRAN and evolutions of UTRAN should be seen as non-limiting example.
In the evolutions of the present mobile communication systems, often referred to as E-UTRAN (Evolved UTRAN) several different radio resource management (RRM) techniques are introduced to meet the high target bit rate requirements. Typical example of RRM functions that will be used in E-UTRAN are admission control, handovers, inter-cell interference coordination and avoidance, load balancing etc. In E-UTRAN, these RRM functions are executed in a distributed manner. This means they reside inside the base station, in UTRAN refereed to as Node B and in E-UTRAN eNode B. In the following these terms are used interchangeably. The efficient execution of RRM functions requires a number of measurements as input to RRM algorithms. Several of these measurements may be performed internally by the Node B itself. However, some measurements results are to be reported to the Node B either from other neighboring Node Bs or from other network nodes such as access gateway.
One important RRM function is the radio admission control or simply admission control. In E-UTRAN admission control will be performed at the eNode B where all radio resource related information resides, see 3GPP TS 25.912. As stated in TS 25.912, the admission control process should take into consideration the overall resource situation in a cell of the communication system. For simplicity the overall resources can be classified into three main categories:                Hardware resource usage        Radio resource usage        Transport network resource usage        
The radio resources include downlink transmitted power, downlink channelization code usage and uplink received total wideband power (RTWP). The transport network includes the resources on the fixed part of the radio access network, namely X2 (Node B—Node B interface) and S1 (Node B—access gateway (AGW) interface) interfaces. Both X2 and S1 interfaces are further split into user and control planes, i.e. X2-U/X2-C and S1-U/S1-C respectively.
It is important to note that admission control refers to the admitting of radio bearers (or calls or connections) at call setup as well as at handover (i.e. on going connections).
Due to the location of the admission control at the Node B, the usage of the first two sets of resources, hardware and radio resources, can be internally determined by the Node B itself. Similarly the transport network load (i.e. load on S1 and X2) in the downlink can also be internally determined in the Node B. However, equally important is the uplink transport network load, which needs to be signaled to the serving eNode B for the purpose of admission decisions.
In WCDMA the admission control decision generally considers the availability of radio resources such as transmitter carrier power, RTWP and channelization code. This is because the radio resources are generally assumed to be the major bottleneck. The transport network resources are on the other hand believed not to be the limiting factor. This is further based on the assumption that operators have sufficient capacity on the fixed interfaces such as Iub (Node B—RNC interface) or Iur (RNC-RNC interface) to admit new radio bearers provided radio resources are available. On the contrary the radio bearers can be blocked or dropped due to insufficient transport network resources, i.e. lack of resources on S1 and X2 interfaces in E-UTRA, wherein S1 is the main bottleneck, or Iub/Iur in UTRA. This is especially due to the fact that over the last few years in UTRAN due to the introduction of sophisticated radio network techniques and advanced UE receivers the bit rate over the radio interface has increased dramatically from 384 kbps to several Mbps. For efficient end-to-end performance the resource allocation on transport network level should match with the resource assignment on the radio interface.
In WCDMA admission control is done in the RNC. This means that uplink transport network load on Iub (Node B—RNC) can be internally measured in the RNC while downlink transport network load on Iub (RNC—Node B), which should be measured in the Node B, should be reported to the RNC. However, currently there is no detailed reporting of downlink transport network load from Node B to RNC. Similarly there is no reporting of uplink transport network load on Iur interface (RNC-RNC) from the target RNC to the serving RNC. Only ‘congestion status’ based on frame loss or delay at transport network is reported by SRNC to Node B, see 3GPP TS 25.427, “UTRAN Iur/Iub interface user plane protocol for DCH data streams”.
Although this allows a Node B to reduce the data rate in case there is congestion, the congestion indication estimation is also implementation dependent. Due to the lack of a detailed reporting mechanism, the congestion status reporting is insufficient for an efficient admission control.