MXPA06007669A - Radio resource management in wireless local area networks - Google Patents

Abstract

A method for radio resource management (RRM) in a wireless local area network (WLAN) having an access point and a station begins by obtaining a first group of parameters from a current traffic channel. Measurements from all available channels are taken for a second group of parameters. The radio resources of the WLAN are autonomously managed by selectively invoking at least one RRM algorithm that uses at least one parameter. A RRM algorithm may be invoked based upon results produced by a previously executed RRM algorithm, whereby RRM algorithms may be continuously invoked such that the radio resources are autonomously managed.

Description

HANDLING OF RADIO RESOURCES IN WIRELESS NETWORKS OF LOCAL AREA FIELD OF THE INVENTION The present application refers, in. general, to methods and systems for managing radio resources (RRM) in wireless local area networks, and more particularly to RRM procedures for self-configuring a network.

BACKGROUND OF THE INVENTION Wireless communication systems are well known in the art. In general, such systems comprise communication stations that transmit and receive wireless communication signals with each other. Depending on the type of system, communication stations are typically one of two types: base stations or wireless transmit / receive units (WTRUs), which include mobile units. The term "base station", as used herein, includes, but is not limited to, a base station, a Node B, a site copter, an access point, or other interface device in a wireless environment. which provides the WTRUs, with wireless access to a network with which the base station is associated. The term "WTRU", as used herein, includes, but is not limited to, a "user" axis equipment, a mobile station, a fixed or mobile subscriber unit, a person searcher, or any other type of device capable of operate in a wireless environment. WTRUs include communication devices, such as telephones, video telephones, internet ready telephones with network connections. In addition, the WTRUs also include portable personal computing devices, such as PDAs and calendar computers with wireless modems that have similar network capabilities. WTRUs that are portable or can change locations in another way, are referred to as mobile units. Typically, a network of base stations is provided where each base station is capable of establishing concurrent wireless communications with appropriately configured WTRUs. Some WTRUs are configured to establish wireless communications directly with each other, that is, without being retransmitted over a network via a base station. This is commonly called wireless peer-to-peer communications. The WTRUs can be configured for use in multiple networks with either network or peer-to-peer capabilities. A type of wireless system, called a wireless local area network (WLAN), can be configured to establish wireless communications with WTRUs equipped with WLAN modems that can also establish peer-to-peer communications with similarly equipped WTRUs. In a WLAN, uiia WTRU is known as a station and a base station is known as an access point. There are two prevalent ways of implementing wireless communications in WLANs and other networks: an infrastructure mode and an ad hoc mode. In the -e infrastructure mode, the WTRUs establish wireless communications through a base station that serves as an access point to the network infrastructure. The communications are coordinated and synchronized through the base station. A configuration like this is also called a basic service set - (BSS) within WLAN contexts. In opposition to the infrastructure mode, the ad hoc mode does not use the network infrastructure. The ad hoc mode operates with peer-to-peer communications and is called an "independent BSS". A popular wireless LAN environment with one or more WLAN access points, ie, base stations, is built according to the 802.11 family of IEEE standards. Typical applications for this type of system include active zones (eg, airports), domestic use, and commercial use. As these systems become more and more prevalent, there is a need to simplify the operation and maintenance of the systems. Many current systems require significant experience and understanding on the part of the user. In a commercial environment, a radio cell planner is required to plan the deployment of the system in order to avoid interference and capacity issues. In a home system, a user must have sufficient knowledge to avoid interference from other home devices such as Bluetooth devices, microwave ovens, cordless phones, and other neighboring WLAN systems. The nature of the interference varies in terms of time and implies that the sophisticated user or radio cell planner is required to adapt the system periodically in order to combat the changing interference. Since this is very unrealistic and therefore, there is a need to automatically manage the WLAN system based on the changing environment. The present invention meets two main requirements: (1) self-configuration and ease of deployment and (2) increased capacity and contiguous coverage. To facilitate self-configuration and ease of deployment, it is convenient to provide an access point (AP) that, when activated, automatically selects optimal operational parameters, such as transmission power, frequency, energy detection threshold, etc. , where minimum configuration data or no configuration data of the installer is required. In addition, it would be convenient - for the AP to periodically monitor its environment and adjust the various parameters to optimize aggregate performance and provide predictable and contiguous coverage.

THE INVENTION A method for managing radio resources (RRM) in a wireless local area network (WLAN), which has an access point and a station, starts by obtaining a first group of parameters from a current traffic channel. Measurements are taken from all available channels for a second group of parameters. The radio resources of the WLAN are handled autonomously by selectively invoking at least one RRM algorithm. that uses at least one parameter. A RRM algorithm can be invoked based on results produced by a previously executed RRM algorithm, so the RRM algorithms can be invoked continuously in order to autonomously manage the radio resources. A self-configuring access point (AP) includes a measurement device, an automatic channel and power selection device, a load balancing device, an interference management device, and a link controller. The measuring device measures a group of parameters of an environment of the AP. The automatic channel and power selection device determines transmission power levels and selects channels based on the parameters. The load balancing device balances the load between the APs with base-to the group of parameters and does not use inter-AP communication. The interference management device is used to compensate for external and internal interference based on the group of parameters. The link controller monitors the downlink quality and adjusts the programming and data speed. An integrated circuit for managing radio resources (RRM) in a wireless local area network (WLAN), which has an access point (AP) and a station, includes means of obtaining .to obtain a first group of parameters of a current traffic channel; measurement means taking measurements of all available channels for a second group of parameters; and managing means for managing the WLAN radio resources autonomously by selectively invoking at least one RRM algorithm that uses at least one parameter.

BRIEF DESCRIPTION OF THE DRAWINGS A more detailed understanding of the invention can be had from the following description of a preferred embodiment, given by way of example and to be interpreted together with the accompanying drawings, wherein: Figure 1 is a general diagram of an RRM algorithm architecture in accordance with the present invention; Figure 2 is a general timing diagram for the RRM algorithm architecture shown in Figure 1; Figure 3 is a top plan view of a system design for an external interference use case; Figures 4-A and 4-B are flow charts showing the actions carried out by access points in the use case shown in Figure 3; Figure 5 is a top plan view of a system design for a use case of a meeting room on an office base; and Figure 6 is a flow diagram showing the actions carried out by access points in the use case shown in Figure 5.

DETAILED DESCRIPTION OF THE PREFERRED MODALITIES The present invention is a distributed radio resource management (RRM) system that allows, collectively, an optimal performance of a WLAN system. The present invention is capable of operating within the following restrictions: it fully complies with the 802. lla / b / e / g, without inter-AP communication, co-existence with typical APs, without special requirements in the stations (i.e. , without information, special measurement of the stations), and without a centralized controller. However, the invention is not limited to these restrictions and may be applied if one or more of these restrictions is removed. The decisions of the present invention are based on the fact that the AP receives and monitors. Every action carried out by individual APs does not come together to form a chaotic and unstable system. The system is designed so that each AP works in unison with the other APs, even when inter-AP communication is not used. The present invention is comprised of four main functions: Automatic Channel and Power Selection, Load Balance, Interference Handling, and Link Control. Together, these four functions operate in unison to form a highly efficient and robust RRM system.

I. Automatic channel and power selection Automatic channel and power selection (APCS) is used both when the AP is activated and during a steady state operation. This function automatically determines the baseline coverage area and the frequency channel establishes the start. From there, it periodically monitors the surrounding environment in order to adjust these parameters as necessary (such as when there are physical changes in the environment, installation or de-installation of a new AP, etc.). The baseline coverage area corresponds to the area within which coverage acceptable to the stations must be provided, and is defined in terms of path loss at its limit, called the baseline range. This internal parameter is determined through • a path loss detection procedure, which estimates the path loss from this AP to neighboring APs by monitoring the available channels. The baseline range is used as one of the three inputs in the configuration of the current transmission power of the AP. The other two inputs are determined by the load balancing function and the interference prevention and compensation function. These entries contemplate adjustments in the coverage area and received power required, respectively. The baseline range is also used as one of several inputs in the energy detection threshold configuration (ED) used in the channel vacancy estimation procedure (CCA), which is used by the AP to determine when to attempt a transmission and a reception of packets.

II. Load balancing Load balancing is used to balance the load across the APs and frequency channels. It is comprised of two complementary mechanisms, the load balance of the AP and the channel load balance. The load balance of the AP adjusts the coverage area of the AP. A range adjustment is applied in the configuration of the current transmission power in order to correct several imbalances between the load of the selected AP and the load in neighboring APs, independently of the frequency channels used by these APs. The main use case for this function is a meeting room scenario, where a large number of people are in a conference room for a short period of time. This function helps to manage the increased load of the AP that provides service to the area of the conference room by temporarily increasing the coverage area of the neighboring APs and reducing the coverage area of the APs in service. This function provides benefits in two ways: the stations currently served by the loaded AP may be better served by one of the neighboring APs, and the current stations in the loaded AP will benefit from better access to the medium due to the discharge of one or more stations to the neighboring APs. This scenario will be analyzed in more detail below. The channel load balance is used to equalize the load between different frequency channels. This is carried out periodically by checking the load on the APs using different channels. A decision can be made to use a frequency channel used by slightly loaded neighboring APs and the channel change is carried out, when there is no activity in the BSS served by the AP. Both load balancing mechanisms are independent and provides a constructive improvement in scenarios where the load is not balanced through channels and / or APs.

III. Prevention and compensation of interference "The prevention and compensation of interference (ICA) is used to compensate for external and internal interference." The ICA function is comprised of three procedures: slow interference estimation, rapid interference estimation and frequency selection escape . In general, the goal of a slow interference estimate is to estimate slowly and continuously the received power required for an acceptable quality. The required received power is used as one of three inputs in the configuration of the current transmission power of the AP. This is done through the monitoring of successful and failed transmissions in order to determine the power received at the stations to achieve an acceptable data rate. The goal of the rapid interference estimation procedure is to quickly adjust the received power required to respond to sudden large changes in external interference due to microwave ovens, elevators, etc. Interference is determined by monitoring the received signal strength indicator (RSSI) when the packet has not been detected. In cases where the BSS is experiencing situations of excessively high congestion or when the interference is intolerable, an attempt is made to select another frequency channel. The frequency channel escape procedure monitors the deferral rate, the packet error rate (PER), and the interference. Since an interruption in service is required to change the frequency channel, only the channel is changed if the current load and / or the interference are unbearable.

IV. Link control Link control is used to monitor the downlink quality perceived by the channel, and to adjust both data rate and programming. The link control is composed of two procedures: the speed control and the programmer. The speed control adjusts the data rate based on the perceived quality of the station. - Lost confirmations will reduce the instantaneous speed. There is also a speed recovery procedure to recover the speed in positive confirmations. In addition, the current charge of the medium will influence the rate of speed reduction and recovery. The programmer tries to maximize the use of the medium by prioritizing transmissions of higher data rates over transmissions of lower data rates. The§. 'Transmissions of lower data rates use more of the medium than transmissions of higher data rates for the same amount of data. Therefore, in terms of maximizing performance, it is beneficial to prioritize transmissions of high data rates. However, this scheme can induce an unacceptable delay for stations with lower data rates. To minimize this delay, the current delay of the users of lower data rates is considered together with the priority in the choice of the next packet to be sent. The 802. lie standard allows the prioritization of delay-sensitive services over others such as voice and video transmission in real time. Programming based on the 802. lie and admission control allows the AP to prioritize and manage station requests for media use. These functions help proactively 'for the AP to understand the maximum bearable load. At 802. lie, station orders access the medium providing information such as the average data rate required. This helps the AP estimate current and future loads in the middle, allowing precise admission control decisions.

V. Generalities on Algorithm Architecture, Interactions and Timing Figure 1 is a diagram showing a general view of a RRM system 100 constructed in accordance with the present invention. The inputs to the system 100 are derived from the live traffic in the current channel 102 and the measurements taken during a period of silence 104. The measurements 104 are taken when the AP is not transmitting and are taken through all available channels. The inputs 102, 104 are supplied to the various algorithms 110-122 that make up the general RRM system 100. In Figure 1, the rectangles represent inputs and outputs to / from the algorithms or procedures and the rectangles of rounded angles represent algorithms and / or procedures. The procedures that require relatively fast reaction times, such as speed / programming control, power control (rapid interference estimation), EDT control and frequency selection escape, monitor the current channel traffic. The remaining procedures such as power control (path loss detection), power control (load balancing), and frequency selection optimization, which have relatively slow reaction times, are based on measurements taken during the period of Silence, the inputs and outputs are well coordinated between the various algorithms and procedures. For example, the current range determined by the path loss and load balancing discovery procedures are used by the EDT control and frequency selection.

A speed / programming control algorithm 110 receives confirmations (ACKs), CCA thresholds and transmission data rate of the current channel 102. The speed / programming control algorithm 110 attempts to establish the transmission data rate given the current operating conditions . Reacts almost instantaneously (in general, in less than a second) to package error rates (that is, one or two lost ACKs) and channel utilization, and thus, their actions are almost independent of the other procedures. Its operating environment is influenced by the other procedures, which try to improve the transmission speed such that, on average, the transmission speed is high. For example, the power control algorithm (ICA) 112 attempts to adjust the power based on several factors including an average data rate. A power control algorithm (ICA) 112 receives RSSI values, ACKs, the transmission data rate, "" and CCA thresholds of the stream channel 102, and receives RSSI measurements and CCA thresholds from the silence period measurements 104. The Power Control Algorithm (ICA) 112 estimates and adjusts a perceived interference in the stations and produces a required received power value 130, which is passed to a first adder 140. The Power Control Algorithm (ICA) 112 includes two parts : a fast power control and a 'slow power control. The fast power control algorithm reacts in response to great sudden interference. It gathers measurements on the current channel 102 and operates periodically (every second approximately) or as necessary, to adjust the received power value 130 required. The slow power control algorithm reacts based on the perceived quality in the station. It gathers measurements on the current channel 1O2 and operates periodically (every minute, approximately) or as necessary, to adjust the received power value 130 required. A power control algorithm (path loss detection) 114, receives measurements of the period of silence of the RSSI 104. The power control algorithm (path loss detection) 114 attempts to determine the optimum coverage area of the cell by monitoring the transmissions of the neighboring AP on all channels. The range of the cell is independent of the channel. The frequency used and only depends on the path loss to neighboring APs. The power control algorithm (path loss detection) 114 produces a base line range value 132 and passes this value to a second summer 142. When the system is in a steady state, the algorithm 114 periodically gathers the measurements of the period of silence 104, and updates the baseline rank value 132. During the discovery of a new AP, algorithm 114 gathers measurements of the new AP during the silence period and updates the baseline rank value 132. The new AP It transmits stronger packages more frequently, which reduces the collection time required to approximately one minute. A power control (load balancing) algorithm 116 receives RSSI values and packet durations from the current channel 102, and receives ACKs and CCA thresholds from the silence period measurements 104. The power control algorithm (load balancing) 116 is used to adjust the coverage area in order to correct important imbalances between the load of this AP and the load in neighboring APs. The load balance is made through APs and is independent of the frequency channel. The power control (load balancing) algorithm 116 produces a range adjustment value 134, which is passed to the second adder 142. An energy detection threshold (EDT) control algorithm 118 receives error rate information from packet (PER) and deferral velocity of the current channel 102. The EDT control algorithm 118 attempts to determine a threshold value EDT 154 such that both packet transmission and reception are optimized. This is mainly based on PER and deferment speed. The threshold value of EDT 154 is limited by the current range of the cell and the sensitivity of the receiver. This algorithm runs relatively fast, making it independent of the actions carried out by other procedures. A frequency channel change causes the EDT to reset the EDT threshold - the minimum value (receiver sensitivity). Any change in the current range value 150 by the power control algorithms 114, 116 affecting the current configuration of the EDT 154 threshold value will be adjusted within about one second. A frequency selection (optimization) algorithm 120 receives RSSI measurements, CCA thresholds, and ACKs from the silence period measurements 104. The frequency selection (optimization) algorithm 120 is used to optimize the use of available channels among the APs. It performs a type of load balancing through channels instead of through APs. This ensures that the actions carried out by the power control algorithm (load balance) 116 and the frequency selection algorithm (optimization) 120 are independent and non-conflicting. For example, an action carried out by the power control algorithms to increase or decrease the coverage area of an AP is based on measurements across all channels, and therefore, it is valid for any channel available for this AP. The frequency selection (optimization) algorithm 120 changes to a new current channel 156 when there is no activity in the channel. A frequency (escape) selection algorithm 122 receives PER information and deferral rate from the current channel 102, and receives RSSI, CCAs, and ACKs values from the silence period measurements 104. The frequency selection (escape) algorithm 122 reacts to intolerable levels of interference and congestion in situations where the AP power increase (rapid and slow interference estimation), the increase / reduction of the ED threshold (EDT control), or the reduction of transmission data rate (control speed / programming) would not help. The frequency selection (escape) algorithm 122 reacts in about 30 seconds once invoked and changes to a new current channel 156. Once the current channel 156 is changed, a rewind of about five minutes is performed before selecting a new channel. The second adder 142 takes the rank of baseline 132 and the range setting 134 as inputs and produces a value of current range 150. The value of current range 150 is supplied as the second input for the first adder 140, which uses the power received required 130 as a first input, and produces a transmit power value 152. The current range value 150 is also supplied as - on input to the EDT control algorithm 118, the frequency selection (optimization) algorithm 120 and the frequency selection (escape) algorithm 122 according to what has been described above in relation to the respective algorithms.

Figure 2 shows the operating frequency of the various algorithms. The present invention is designed to react relatively quickly to its changing environment. New APs are discovered within about one or two minutes, and the system is capable of clearing significant load imbalances within five minutes to contemplate the "meeting room" scenario, for example. In addition, fast-reaction algorithms such as frequency selection escape, react every 10 seconds to significant interference or congestion situations.

SAW. Use case 1: Severe External Interference The following use case illustrates the sudden presence of severe external interference. The basic network design is illustrated in Figure 3, where four APs (BSS 1 to BSS 4) are configured in a 50 m x 50 m building. The AP4- is located next to a small office kitchen, where a microwave oven is located. Certain assumptions are made about the interference generated by the microwave oven, based on empirical evidence. The interference generated by the microwave oven is the highest in channel 11, lowest in channel 6, and very low in channel 1. In addition, the interference is only unbearable when located close to the microwave oven (ie, within BSS 4). ).

Before using the microwave oven, the system is in the following state: all the BSSs are operating at a similar average load, with high satisfaction for all stations served; all APs are transmitting at 5 dB below their maximum power configuration; and all stations are transmitting at full power. The initial channel assignment for each BSS is given in Table 1: Table 1: Initial channel assignment for each BSS Once the microwave oven is turned on, the BSS 4 perceives an intolerable level of interference, while the interference levels in the BSS 1 and the BSS 3 increase. In AP 1 and AP 3, the following sequence of events, as shown by Figure 4-A. The level of perceived interference increases due to microwave radiation, raising the noise floor of the receiver by approximately 3 dB for the APs and stations (weight 402). Packet transmission errors are perceived in the downlink (DL; step 404). The speed control algorithm immediately attempts to solve the interference problem by reducing the packet transmission rate (weight 406). The power control algorithm (interference estimate) becomes aware of the interference increase and increases the transmit power of the AP by 3 dB (step 408). Eventually, the speed control recovers the original transmission rates for each station (step 410). In AP 4, the following sequence of events occurs, as shown in Figure 4-B. The perceived interference level increases significantly due to the microwave radiation, raising the noise floor of the receiver by approximately 20 dB for the APs and the stations (step 420). Many packet transmission errors are perceived in the DL and the uplink (UL, step 422). The speed control algorithm immediately reduces the speeds to all stations (step 424). The power control algorithm becomes aware of the interference increase and increases the transmit power of the AP to the maximum transmit power of the AP (step 426). Since an excessively high packet error rate is still perceived, the frequency selection escape algorithm is triggered. The AP changes its channel from channel 11 to channel 1, where the microwave oven generates much less interference (step 428). All stations are disassociated, and eventually re-associate (step 430). The power control algorithm reduces the transmit power according to the level of perceived interference on channel 1 (step 432). The final channel assignment for each BSS is given by Table 2.

Table 2: Assignment of final channel for each BSS VII. Use case 2: Scenario of a Sala efe Meetings Suppose there is a system of four WLAN APs covering an area of 50 m x 50 m, each AP covers approximately 25 x 25 m. The area is divided, mainly, into offices, with a large conference room and a small conference room. Each office is an office for one or two people. Each employee has a laptop with wireless LAN access. The APs are located more or less in each quadrant of the area as shown by Figure 5. The main assumptions in this scenario are that the APs are uniformly balanced, each assuming a quarter of the total load, and initially operating in the channels shown in Table 3. The total load in each AP is slight, with approximately 10% of the available capacity of the APs used.

Table 3: Initial channel allocation for each AP The following events and actions are produced, as shown in Figure 6. A large meeting is held in the two conference rooms at ULQ. Suddenly, the load increases for the ULQ AP due to increased activity, while the load on the other quadrants decreases (step 602). In five to ten minutes, the power control (load balance) has collected enough measurements to determine that it needs to reduce the range of the affected cell (step 604). Similarly, neighboring APs also detect an increased load in ULQ,. and thus *, increase the range of its APs (step 606). They may face doing so given that the load is light in their coverage areas. The increase in transmission power immediately benefits those stations that decided to connect to one of the neighboring APs despite their less favorable location. In parallel, the frequency selection optimization in the LRQ AP (which is using the same channel as the ULQ AP), finds that the activity in the other channels is much lower than the channel it is currently using and makes a decision to change the frequency to channel 6 or to channel 11 (step 610). The real change will be made only when there is no activity in the AP of LRQ. Stations in the marginal areas of ULQ could be re-associated with other AP quadrants (step 612). Some stations include built-in load balancing functions, and could then easily choose a less loaded AP, as the coverage area has been increased. The RRM algorithms previously described can be used by an AP. The components of the AP that perform RRM can be an integrated circuit (IC) alone, such as a specific application integrated circuit; multiple ICs; discrete components; or a combination of IC (s) and discrete components. i Although the features and elements of the present invention are described in the preferred embodiments in particular combinations, each feature or element can be used alone (without the other features and elements of the preferred embodiments) or in various combinations with or without other features and elements. of the present invention. While specific embodiments of the present invention have been shown and described, those skilled in the art can make many modifications and variations without departing from the scope of the invention. The above description serves to illustrate and not to limit the particular invention in any way.

Claims (8)

1. CLAIMS 1. Method for managing radio resources (RRM) in a wireless local area network (WLAN), which has an access point (AP) and a station, the method characterized in that it comprises the steps of: obtaining a first group of parameters from a current traffic channel; take measurements of all available channels for a second group of parameters; and managing the radio resources of the WLAN autonomously by selectively invoking at least one RRM algorithm that uses at least one parameter. Method according to claim 1, characterized in that the step of taking measurements includes taking measurements during a period of silence when the AP is not transmitting. Method according to claim 1, characterized in that the handling step includes invoking a RRM algorithm based on the results produced by a previously executed RRM algorithm, so the RRM algorithms can be continuously invoked in such a way that the resources of radio are handled autonomously. Method according to claim 1, characterized in that at least one RRM algorithm is selected from the group consisting of: speed / programming control, power control, energy detection threshold control and frequency selection. 5. Method according to claim 1, characterized in that at least one parameter is selected from the group consisting of: confirmation, channel vacancy estimation, transmission data rate, received signal strength indicator, packet duration, package error, and deferment speed. 6. Self-configuring access point (AP), characterized in that it comprises: a measuring device for measuring a group of parameters of an AP environment; an automatic channel and power device to determine transmission power levels and select channels based on the parameters; a load balancing device for balancing a load between APs based on the group of parameters and not using inter-AP communication; an interference handling device for use in external and internal interference compensation based on the group of parameters; and a link controller to monitor downlink quality and adjust the programming and data rate. 7. Self-configuring access point (AP), characterized in that it comprises: measurement means for measuring a group of parameters of an AP environment; automatic power and channel selection means for determining transmission power levels and selecting channels based on the parameters; load balancing means for balancing a load between APs based on the group of parameters and not using inter-AP communication; interference management means for use in compensation of external and internal interference based on the group of parameters; and media cié control of link to monitor quality of downlink and adjust the programming and speed of data. 8. Integrated circuit for management of radio resources (RRM) in a wireless local area network (WLAN), which has an access point (AP) and a station, the integrated circuit is characterized because it comprises: means of obtaining to obtain a first group of parameters from a current traffic channel; measurement means for taking measurements of all available channels for a second group of parameters; and managing means for managing the WLAN radio resources autonomously by selectively invoking at least one RRM algorithm that uses at least one parameter.