A control method that enhances or rejects users to access network resources, usually based on certain groups belonging to the user's account or user.
Mobile Communication Terms
Three mainstream standards of the third generation mobile communication system are based on, different, different users in the TDMA network, and the CDMA network is applied. " The concept of soft capacity, the number of users accommodated in various cells in the CDMA network depends on the total interference accepted by the community base station.
In the CDMA system, each additional new or switched user is increasing, the interference level will increase, according to all, in order to ensure the integrity of the link, each move Taiwan should appropriately improve its transmit power, this adjustment, in turn increases the interference level necessary to overcome the next mobile station. This process is self-repeating until a mobile station does not have sufficient power to overcome the interference level, and cannot obtain satisfactory voice quality at the base station. At this time, the communication link is forced to interrupt, and the system reaches its capacity limit. Overweight interface load will reduce the coverage area of the cell to the planned value, and the existing connection service quality is not guaranteed, and the system can also cause the system to be unstable, which in turn can cause a drop.
So in the resource management of the next-generation wireless network system, access control is essential, it is essential for avoiding business load overload to ensure the stability of the system is critical.
A new connection request is accessed and the core task of access control is constituted. The principle is that the new connection of access should not be at the expense of the service quality of the existing connection. Before accessing a new connection, the access control must check if the request access will sacrifice the quality of the planned coverage or existing connection. Effective and perfect access control algorithms are restricted to current system capacity, thereby greatly guaranteeing communication quality of the connected connections and maximizing system resource utilization. That is, when the cell capacity is in a saturated state, it is no longer receiving the new connection request to ensure the QoS requirements of the user; when the cell capacity is not saturated, the new connection is accepted as much as possible while ensuring that the user QoS requires. Request to make full use of wireless resources.
Overall, the purpose of access control is: access or reject the user's call request; avoid system overload; decide whether to access by interference and radio resource measurement; optimize network income.
Access Control Basic Decution Based on
CAC control target contains two aspects: First to meet the user QoS requirements; second to maximize the use of communication system resources . The CAC algorithm uses different receiving decision criteria based on different target requirements. Guidelines that meet QoS requirements include call blocked probability and switching line probability should be less than or equal to the corresponding maximum allowable value; through the actual overload probability of less than or equal to equal to equal to equal, the maximum acceptable user number; according to the number of error frames in total time slot The ratio of the total receiving frame should be less than or equal to the maximum allowable error rate; in the cached system, it can also be determined whether or not the user delay is determined to receive or not. Maximize the receiving area of the communication system resource criteria can be summarized as the system has less than or equal to the total resources of the system's existing resources and connection requests.
CDMA is an interference restricted system, and its CAC is divided into two cases of downlink and uplink. Downlink adopts power-based guidelines: connection users have used transmit power and call requests and should be smaller than that of the base station allows total transmit power. This algorithm is clear, and since it is easy to achieve a base station emission power. The uplink can be criteria based on the number, power, interference, bandwidth or remaining capacity. The call request is received only when the upper downlink is satisfied.
Accepted Control Need to consider problems
Resource reserved
during cellular mobile communication , Interrupt one ongoing call, which is greater than the negative impact of rejecting a new call request, and therefore in the accepted control, switching is usually given a higher priority. The existing methods are mostly based on the protection channel mechanism, ie, reserved a part of the capacity is only for switching allocation. In order to better improve performance, there is a series of extended forms, such as allowing switching or new requests waiting in line to wait in a probabilistic form to receive new requests in some probability. The key to the protection channel mechanism is to determine the optimal reserved capacity for switching. The capacity is reserved, and the mandatory termination probability is increased, the performance of the switch is reduced; the capacity is reserved, the blocker probability of the new request is increased, and the utilization rate of the bandwidth is lowered. When the network traffic is changed, the simple protection channel mechanism is difficult to adapt. Adapt to the real-time change of the network traffic, according to the current system's load dynamic, adaptively adjusted receiving control algorithm research has become a current research hotspot.
User Mobile Model and Service Model
In the actual system, the new user appeared in the fixed area, and its mobile direction is random, but it is Basic law. Calls for overlambient switches, valid resource reserved programs should consider the user's mobile model. The bandwidth is presented according to the history of user movement or by predicting the mobility of the user, it is concerned.
Multi-service support
A good program should take into account the characteristics of different business calls, and differentiate. Basic processing methods are more priorities that have higher priority services than low priority services.
QoS parameter
In call receiving control, the most popular service quality parameters are call blocked probability and switch interrupts. Probability. This two parameter values are usually utilized to verify the performance of the scenario. As the adaptive business uses the business, different transmission rates can be employed. When the system is loaded, it can be transmitted at a larger rate; the system load is loaded, and some new parameters are transmitted, such as downgrades. Rate and elevation frequency.
Conside by the neighboring cell interference
The newly accessible user is interfered with the cells in this cell, and the neighboring cells are interfered, especially When the newly connected user is in the edge of the cell, the receiving the decision not only checks the interference of the cell, but also checks the interference of the neighboring cell.
LTE Access Control
Access Control is the system to avoid the system overload, and determine the terminal access, and the access control is determined to receive or refuse to establish a new Wireless bearer. Access control needs to be judged based on the load conditions of the network, resource usage, service user QoS level, and the priority of the new access user and the parameters such as QoS levels. The purpose of access control is to improve the utilization of wireless resources, while ensuring that existing users' QoS is unaffected, guarantee high priority users.
Access control determines according to the number of users, the system can set the user number threshold. When the number of users reaches the threshold, the system is to determine the access control according to the new user's access priority. If the priority of the new access user is relatively low, new users are not allowed to access. If the new access user is a high priority user and meets the preemption conditions, the system can allow new users to access but at the same time, the low priority user in the service user switches to other cells, or the system can redirect the new access user to Other cells.
In addition to the number of access controls based on the number of users, there is a system resource-based access control method. Access control based on system resources is mainly for users with GBR service QoS. When there is a GBR service user access, the system will measure the system resource. If the user can meet the GBR requirements of the user, if it is met, the user is allowed to access, otherwise it is necessary to perform resource adjustment and evaluate whether the adjustment can be met. The user's GBR requirement. The resource adjustment method is to reduce the GBR and Non-GBR users in the service user to save system resources to new access users. If the system resource can meet the GBR user access after the reduction processing, the user is allowed to access. Otherwise, if the system resource does not meet the new user access request, the system rejects the user access request, or redirects the user to other cells.
Since the access control algorithm is not clear in the protocol, it is mainly based on the different implementations of the device manufacturers, so various methods may be used.