What Are the Different Types of Interactive Resources?

Radio Resource Management (RRM): Under the condition of limited bandwidth, it provides service quality guarantee for wireless user terminals in the network. Its basic starting point is the uneven distribution of network traffic and channel characteristics due to channel weakness and interference. In the case of fluctuations, the flexible allocation and dynamic adjustment of the available resources of the wireless transmission part and the network can maximize the utilization of the wireless spectrum, prevent network congestion, and keep the signaling load as small as possible.

Chinese name: Radio Resource Management
Foreign name: Radio Resource Management

Short name: RRM
Features: Prevent network congestion
Applied discipline: Communication

Radio Resource Management Overview

1.1 Composition of Radio Resource Management 1.1

The research contents of radio resource management (RRM) mainly include the following parts: power control, channel allocation, scheduling, handover, access control, load control, end-to-end QoS and adaptive coding and modulation.

Figure 1 Schematic diagram of wireless resource management architecture

1.2 Radio Resource Management 1.2 Difference

Depending on the object, there are two different divisions of radio resource management:

(1) Connection-oriented RRM. Ensure the QoS of the connection and minimize the wireless resources occupied by the connection. At this time, channel configuration, power control, and handover must be considered. For each connection, create an instance to handle the resource configuration of this connection as needed.

(2) Cell-oriented RRM. On the premise of ensuring the stability of the cell, it can access more users and increase the capacity of the entire system. At this time, it is necessary to consider code resource management and load control. Create an instance for each cell to handle resource management for that cell.

The basic process of implementing radio resource management or control is: measurement control measurement UE (user equipment), NodeB (node B), RNC (radio network control) measurement report decision, decision resource control and execution.

What RRM needs to do is to ensure the QoS requested by the CN (core network), enhance the coverage of the system, and increase the capacity of the system. To achieve the purpose of RRM, the following items need to be done: channel configuration, power control, handover control, and load control.

Detailed research on radio resource management

Radio Resource Management Power Control

In mobile communication systems, strong near-earth signals suppress far-away weak signals to produce a "far-far effect." The channel capacity of the system is mainly limited by co-frequency interference from other systems or interference from other users in the system.

Schematic diagram of power control Without affecting the communication quality, performing power control to minimize the power of the transmitted signal can increase the channel capacity and increase the battery standby time of the user terminal. Traditional power control technology is mainly based on voice services, and research in this area has been quite extensive, mainly involving centralized and distributed power control, open-loop and closed-loop power control, constant-reception-based and quality-based power control. At present, power control research focuses on data services and multimedia services, and most of them are comprehensive power control and rate control research. The goals of power control and rate control are basically contradictory. The goal of power control is to allow more users to enjoy common services at the same time, while rate control is to increase system throughput as a goal, making individual users or services Has a higher transmission rate. How to meet the different QoS requirements and transmission rates between users, and simultaneously achieve the dual goals of fairness and high throughput is a hot topic at present.

The power control technology used in circuit-switched networks is no longer suitable for IP transmission and complex wireless physical channel control.

Radio Resource Management System, when the IP network becomes the core network, how to perform power control in a packet-switched network has become the main content of power control research. The research on the communication network based on Burst-mode power control and the design of the burst-by-burst communication system have attracted much attention. Combined with joint research on power control and other new technologies, such as smart antennas, multi-user detection technology, error control coding technology, adaptive coding and modulation technology, and subcarrier allocation technology, improving system capacity is also a relatively popular research topic.

Radio Resource Management Channel Assignment

In wireless cellular mobile communication systems, there are three main types of channel allocation technologies: fixed channel allocation (FCA), dynamic

Channel allocation diagram Channel allocation (DCA) and random channel allocation (RCA). The advantages of FCA are easy channel management and easy control of inter-channel interference. The disadvantages are that the channel cannot be optimally used, the spectrum channel efficiency is low, and the traffic between the access systems cannot be uniformly controlled, which will cause spectrum waste. Therefore, it is necessary to use dynamic Channel allocation and coordinated flow control between systems to improve the efficiency of spectrum channel usage. The FCA algorithm proposes a channel borrowing scheme (such as channel reservation borrowing (BCO) and directional channel lock borrowing (BDCL)) to enable the cellular network to change with traffic changes. The idea of the channel borrowing algorithm is to use the channels that are not used by neighboring cells to this cell to achieve the maximum utilization of resources.

DCA can be divided into different allocation algorithms according to different division criteria. DCA algorithms are generally divided into two categories: centralized DCA and distributed DCA. The centralized DCA is generally located in the high-level radio network controller (RNC) of the mobile communication network. The RNC collects channel allocation information of the base station (BS) and mobile station (MS). The distributed DCA determines the allocation of channel resources locally. The complexity of RNC control is greatly reduced, and the algorithm needs to have a good understanding of the state of the system. According to the different characteristics of DCA, the DCA algorithm can be divided into the following three types: traffic adaptive channel allocation, reused divided channel allocation, and interference-based dynamic channel allocation algorithms. DCA algorithm also has DCA based on neural network and DCA based on time slot scoring. The maximum packing (MP) algorithm is another type of channel allocation algorithm that is different from the FCA and DCA algorithms. The DCA algorithm dynamically allocates channels for new calls, but when the channel runs out, new calls will block. The idea of the MP algorithm is: assuming that a channel has been allocated for a new call in a non-adjacent cell, and the channel has been used up at this time, if there is a new call request channel at this time, the MP algorithm (MPA) can Ongoing calls in neighboring cells are packed into one channel, and the remaining other channel is assigned to the new call.

RCA is to randomly change the calling channel in order to reduce the poor channel environment (deep fading) in the static channel, so the interference of each channel change can be considered independently. In order to obtain the required QoS for error correction coding and interleaving technology, it is necessary to continuously change the channel to obtain a sufficiently high signal-to-noise ratio.

Radio resource management scheduling technology

One of the main characteristics of future mobile communication systems is the existence of a large number of non-real-time packet data services. because

Examples of modulation techniques There are different rates for different users. The sum of the rates of all users in a base station often exceeds the channel capacity that the base station can transmit. Therefore, a scheduler must be used in the base station to determine the type of the service according to the user's QoS requirements. Allocate channel resources to different users. Recently, the scheduling technology has been combined with other technologies, such as the integration of scheduling technology and power control, the combination of scheduling technology and soft handover technology, the combination of soft handover technology and call admission control technology, and the scheduling technology has also been extended to real-time data ( Real-time data), and proposed new applications. In addition, in order to provide QoS in the Internet, such as IntServ or DiffServ services, scheduling technology also plays an important role.

Radio resource management switching technology

Handover technology refers to a mobile user terminal moving from one base station coverage area to another during the call.

Switching technology Cover the area or leave the service area of one Mobile Switching Center (MSC) and enter another MSC service area to maintain uninterrupted mobile user calls. Effective handover algorithms can improve the capacity and QoS of cellular mobile communication systems. Switching technologies are generally divided into hard switching, soft switching, softer switching, inter-frequency switching and inter-system switching. The handover technology mainly uses information such as the quality of the network information signal and the user's moving speed as references to determine whether the handover operation should be performed. In addition to the handover techniques given above, the handover techniques being studied are based on channel borrowing and handover based on user location. In the future mobile communication systems, handover technology and mobility management are becoming more and more closely integrated. Since the core network of future mobile communication systems is the IP network, this will inevitably bring new problems and challenges to mobile user handovers. Existing handover algorithms are designed for cellular mobile communication systems, and the Internet protocol was not originally designed for wireless communication environments. To enable handover technologies in future mobile communication systems, existing handover technologies must be modified. The IETF has done a lot of work on mobility management, and proposed and formulated some related standards: such as the macro-mobility and micro-mobility standards.

Radio Resource Management Call Admission Control

Voice admission-based call admission control is a fairly simple matter of deciding whether to accept calls from new users.

Call admission control diagram When the base station has available resources, it can meet user requirements. In the CDMA network, using the concept of soft capacity, the generation of each new call will increase the interference level of all other existing calls, thereby affecting the capacity and call quality of the entire system. Therefore, it is more important to control the calls that access the network in an appropriate way. The 3rd generation and future mobile communication systems require support for multimedia services such as low-speed voice, high-speed data, and video, so call admission control becomes more complex. The requirements for call admission control in future mobile communication systems are: during the decision process, using network planning and interference measurement thresholds, any new connection should not affect the coverage and the quality of the existing connection (the entire connection period). When a connection occurs, call admission control uses load information from load control and power control to estimate the increase in uplink and downlink loads. The change in load depends on parameters such as traffic and quality. If it exceeds the uplink or downlink threshold , New calls are not allowed. The call admission control algorithm gives the transmission bit rate, processing gain, wireless link initiation quality parameters, bit error rate (BER), signal-to-noise ratio (Eb / No), and signal-to-interference ratio (SIR). Call admission control manages bearer mapping, initiates forced call release, and forces switching between frequencies or between systems.

The call admission control algorithms currently under study mainly include the following categories: QoS-based call admission control algorithms, which classify the incoming call services, such as real-time services and non-real-time services, and then separate them Perform different call connections on it; interactive call admission control algorithm; call admission control algorithm based on equivalent bandwidth; capacity-based call admission control algorithm; power-based call admission control algorithm; distributed call admission Control algorithms, etc.

With the support of future mobile communication systems for multimedia services such as data, images, and video, the transmission rate of their services is also getting higher and higher. This requires the study of new call admission control algorithms suitable for high-speed mobile communication systems. In addition, when considering the call admission control of the mobile communication system, the congestion control strategy is also an aspect that usually needs to be considered. Therefore, the call admission control and the congestion control are often studied in combination.

QoS Radio resource management end-to-end QoS guarantee

The traditional Internet network provides "best effort" services, and the IP layer cannot guarantee

QoS guarantee in radio resource management Service QoS requirements, end-to-end QoS guarantee must be achieved through the Transmission Control Protocol (TCP) layer. Although the TCP layer can guarantee a certain QoS, such as reducing the packet loss rate, it still cannot meet the end-to-end QoS requirements of multimedia services such as image and video transmission in wireless systems that require high real-time performance. And the core network of the future mobile communication system will be an IP-based network, which raises new questions on how to provide reliable end-to-end QoS requirements for future high-speed multimedia services on the mobile Internet network. Most current methods of guaranteeing the quality of service (QoS) of mobile IP services do not take into account end-to-end QoS guarantees. The next generation of high-speed wireless / mobile networks requires access to the Internet, supports a variety of multimedia applications, and guarantees QoS for services. However, due to the user's mobility and the unreliability of the wireless channel, the problem of QoS guarantee is more complicated than that of the wired network. Traditional IP networks cannot guarantee the QoS of user services, which has become a huge obstacle to the Internet's development. Therefore, the IETF has proposed two typical guarantee mechanisms for enhancing the QoS performance of existing IPs: Integrated Service / Resource Reservation Protocol (InterServ / RSVP) and DiffServ.

In wireless networks, traditional flow control is not suitable for providing QoS guarantee, because packet loss during wireless channel transmission will be treated as network congestion. UMTS defines 4 types of QoS types: session categories that have strict requirements on the maximum transmission delay, flow categories that have certain requirements on the delay jitter of the end-to-end data flow, interactive categories that require the round-trip delay time, and delay that Background category with very low sensitivity requirements. The network allocates different channel resources for different types of QoS services. In addition, there are several other algorithms to solve QoS, such as wireless link layer solution, TCP connection separation method, TCP stacking solution, socket / gateway solution, etc.

The research content of other wireless resource management aspects such as adaptive coding and modulation, wireless resource reservation is also being further studied and discussed ^[1] .

TDSCDMA Application of Radio Resource Management in TDSCDMA

The TD-SCDMA mobile communication system has obvious advantages in system performance, capacity, and manufacturing costs due to the use of advanced communication technologies such as smart antennas, joint detection, and uplink synchronization. And as having CDMA features

For mobile communication systems, reliable and efficient radio resource management (RRM) strategies and methods are important guarantees for the performance and capacity of CDMA mobile communication systems. The wireless resources in TD-SCDMA system include codeword, frequency, time slot, power and space angle. The reason why this system has high spectrum utilization is that it uses a combination of time division, frequency division, code division and space division, and many others. new technology. In a CDMA-based mobile communication system, the use of smart antenna technology can increase system capacity, reduce interference between users, expand cell coverage, support new services, improve network security, and implement user positioning. Multi-user joint detection and uplink synchronization technology effectively suppress multiple-access interference, so that CDMA systems can accommodate more active users at the same time under the same processing gain. Therefore, the TD-SCDMA system can improve the SINR, reduce the impact of delay spread and fading through the digital signal processing technology of space domain processing or space-time joint processing, and then improve the link quality. The improvement of link performance can more easily provide various new services, such as data services and wireless Internet services that have higher requirements on bit error rates. However, after adopting technologies such as smart antennas, it will definitely involve changes in many network functions, such as radio resource management and mobility management. As the space perspective becomes an available resource, when allocating and managing system resources, we must consider both maximizing system resource utilization and coordinating the relationships between various resources in order to minimize users. Only in this way can the overall performance of the system be guaranteed to be optimal. Due to the expansion of resource connotation and the increase of resource types, especially after the spatial perspective becomes available resources, the system's resource allocation and management algorithms are much more flexible and more complex than traditional mobile communication systems. However, the current research on smart antennas and joint detection technologies is based on the information technology of the physical layer, that is, only the implementation of the technology itself and the link-level performance are studied. The network efficiency involved in them has not been studied. Give full play to the effectiveness of smart antennas and joint detection. Wireless resource management is a combination of information technology and network technology, while the functions of traditional RRM are based on the allocation and adjustment of actual physical resources (hard resource management method). However, after using space-time processing technologies such as smart antennas and joint detection in TD-SCDMA systems, the system adds and derives new logical and virtual resources, and the connotation of system resources has been expanded. Therefore, it is necessary to study and use new wireless The theory and strategy of resource management (soft resource management method, equivalent resource management method). Only by effectively allocating and managing multiple wireless resources in the space-time processing system can we really improve the reuse rate of frequency resources and code channel resources. And the utilization of power resources to achieve the design goals of the system. ^[2]

Radio resource management function

The Radio Resource Management (RRM, Radio Resource Management) function is an important part of the Radio Network Controller (RNC), and its role mainly includes the following three aspects.

(1) To ensure the quality of service (QoS) of users applying for services, including block error rate (BLER), bit error rate (BER), time delay (Delay), business priority level, etc.

(2) Ensure the coverage of system planning.

(3) Make full use of and increase system capacity.

The functions of RRM are mainly calculation, control and resource allocation. It mainly consists of algorithm module, decision module, resource allocation module, wireless resource database and external interface module. The most important one is the algorithm module, including the following functional modules.

(1) Power control (PC, PowerControl) module: consume power resources as little as possible on the premise of maintaining link communication quality, thereby reducing mutual interference in the network and extending the use time of the terminal battery.

(2) Handover Control (HC, HandoverControl) module: to ensure the continuity of mobile user communications, or to transfer users from the current communication link to other cells based on network load and operation and maintenance reasons.

(3) Admission Control (AC, AdmissionControl) module: When a new user or a handover user initiates a call, the network performs an admission control process, the purpose of which is to maintain the stability of the network and the QoS of the accepted user.

(4) Load control (LC, LoadControl) module: continuously calculates the load information of the network and provides this information to other modules. When the network is overloaded, the LC restores the network to a normal state through the combined effects of other modules in the RRM.

(5) Packet Scheduler (PS, PacketScheduler) module: It is used to serve packet data services. The specific scheduling rate is determined by the network load.

(6) Dynamic Channel Assignment (DCA) module: responsible for assigning channels to cells, channel prioritization, channel selection, channel adjustment, and resource integration.

(7) Wireless link monitoring (RLS) module: responsible for monitoring the quality of the wireless link. When the quality of the communication link is detected to be deteriorated, a report is sent to the corresponding RRM module, and degradation processing or degradation recovery processing is performed.

(8) Resource management (RM, ResourceManagement) module: includes code allocation (CA, CodeAssignment), management of logical channel resources and transmission channel resources.

In addition to the modules listed above, RRM also includes a congestion control (CC, CongestionControl) module, a cell selection (CS, CellSelection) module, and a radio bearer control (RBC, RadioBearerControl) module.