SE515509C2 - Adaptive air interface - Google Patents

Abstract

The invention relates to an adaptive air interface suitable for use in a cellular telecommunication system. The air interface contains various kinds of information elements having operating parameters such as framing data, synchronization data, information data and error control data. The adaptive air interface in accordance with the invention includes means for collecting parameter requirements, means for relating the parameter requirements to an input space, means for transforming the input space to an output space, the output space defining the operating parameters of the air interface. Preferably, the transformation means includes a fuzzy logic controller.

Description

30 35 40 515 509 ~~~~ ~ 2 Fig. 4A to F are diagrams of rank functions for output variables.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS The air interface according to the present invention is described below with reference to a mobile telecommunications system, but can be similarly applied to other air interfaces in a manner that is obvious to a person skilled in the art. The adaptive air interface contains a number of parameters and systems which are controlled in an adaptive manner. Some of the features of the adaptive air interface are 0 TDMA or FH-TDMA (Frequency Hopping Time Division Multiple Access) 0 Frame period 0.5-2 ms basis, x (1/8, 1/4, 1/2, 2, 4) determined in an adaptive manner 0 Fast power control at each burst 0 Mobile station (MS) provides return channel response at each burst 0 Network data rate: 32, 64, 128, 144, 192, 384 kb/s 0 Modulation system 2-16 PSK, QPSK, 8PSK/2AM, 16QAM, 64QAM 0 FEC and/or turbo coding 0 Program-controlled parameters, partly by statistical logic 0 Supported modulation bandwidth 25, 50, 100 and 200 kHz 0 Frequency hopping function to improve fading resistance and for to improve C/I performance 0 Supports 64 kb/s PCM and G722 high quality speech coder of 20-7000 Hz, and primary rate 2B+D 0 Adapts to 2-20 ms total process delay requirement Users are classified into 3 different categories 1. slow (stationary or walking) speed 2. medium (fast walking, slow car) speed 3. high (fast car) speed The air interface according to the invention enables adaptability to prevailing situations and scenarios. A number of possibilities arise with the following adaptive parameters in what is called the output space. 0 Frame time 0 Data rate 0 Bandwidth 0 Code rate 0 Duty cycle 0 Mobile station (MS) power 515 509 §¿1j=§:j§-¿=.¿_,= -1 - 3 0 Base station (BS) power The decision behind the parameters is based on measurements, user needs, consideration towards the operator and given resources using an optimization algorithm. These parameter requirements are retrieved by the interface. The requirements are related to the input data or input space which contains the following parameters 0 Mobile speed 0 Delay 0 Distance 10 0 Delay variations 0 Capacity remaining in the mobile station 0 BER (Bit Error Rate) A number of examples are given and an arrangement based on either a state machine or a solution with statistical logic is given to calculate the parameters under varied conditions.

In Fig. 1 a block diagram of the transformation of the input space to the output space is shown. The input space is processed by means of a logic control box which includes rules for the transformation. One way of carrying out the transformation is by means of a state machine.

A state machine has a finite number of states of the input variables which are transformed by means of logical rules into output variables. Below is an example of logical rules in a state machine with finite states.

IF 25 {Mobile speed=Stationary AND Delay < 6 ms AND Distance < 8 km 30 AND Delay variations < 1 us AND Remaining capacity > 0.4 AND 35 BER < l0-6-6} THEN {Frame time = 2ms AND 40 Data rate = 144 kb/s . i ~ . - r 10 15 20 25 30 35 40 . | - . n u 515 509 . . - = - » n AND Bandwidth = 100 kHz AND Code rate = 0.8 AND Duty factor = 45% AND BS power = 22 dBm AND MS power = 6 dBm} Another way is to perform the transformation using a controller with statistical logic. In contrast to the state machine, the controller with statistical logic operates with a number of rank functions u. For each variable, a number of rank functions are defined. The rank functions can take on different values ranging from zero to one and not just the discrete numbers zero and one.

In Fig. 3A to F, a number of rank functions for input variables are illustrated. As can be seen in the figures, each invariant has a set of three rank functions that assume different values for a specific value on the x-axis. The statistical logic controller contains rules for transforming the input rank functions into output rank functions. An example of output rank functions is illustrated in Fig. 4A to F.

For each output variable, a separate value for three output variable rank functions is thus obtained. The statistical logic controller also includes rules for "sharpening" (defuzzification) which provides a sharp value on the x-axis for the set of rank function values.

Since the output values to be used in the air interface can only take on fixed values, an additional quantization operation is performed to obtain the sharp output variables. The sharpening operation and the quantization operation are illustrated in Fig. 2.

The logical rules for the statistical logic controller, also called the statistical rule base, are determined by a detailed study of the specific problems at hand. There are commercially available computer-aided procedures for defining, fine-tuning, and optimizing the statistical rule base.

An example of rules for statistical logic is given below.

IF {Mobile speed = low AND Delay = Medium AND 10 15 20 25 30 35 , . « . :v 515 509 Distance = Medium Delay variation = small AND Remaining capacity = Medium AND BER = Small} THEN {Frame time = Low AND Data rate = High AND Bandwidth = low AND Code rate = high AND Intermittency = Low AND BS power = medium AND MS power = Medium The quantization operation is performed according to the example below: Let x be quantized according to x = {x1, x2,.....xn}. Input xc gives xi, where xi As an example, the output variables can take on the following values: 0 Frame time = {0.5, 1, 2, 4, 8} ms 0 Data rate = {16, 32, 64, 128, 144, 192, 388} kb/s 0 Bandwidth = {25, 50, 100, 200} kHz 0 Code rate = {4/5, 3/4, 2/3, 1/2) 0 Modulation system = {QPSK, SPSK, 16QAM, 8CPM/TCM, 640QAM, 32QAM/TCM,...} 0 Operating mode = {Normal, FH} 0 BS power = {30, 28, 26,...} dBm Optimization of output variables, according to selected cost functions, is carried out in order to e.g. maximize quantities such as capacity and throughput, minimize the power from the base station and the mobile station. The optimization is performed on the following variables: 515 509 6 0 Energy consumption 0 Spectrum usage 0 Data rate 5 0 Quality measured in BER (bit error rate) The cost function CF is based on the following rule _ performance >< quality CF costs performance = data rate 10 kVålltClI I -lO >< where the cost is expressed as an inverse of the spectrum usage x energy consumption, i.e. 1 spectrum usage >< energy consumption cost and

Claims (8)

10 15 20 25 30 '515 509 7 PATENT REQUIREMENTS An adaptive air interface in a telecommunication system, comprising means for obtaining parameter requirements; means for relating the parameter requirements to an input space, i.e. given characteristics of the telecommunication system; means for transforming the input space into an output space, the output space defining the adapted operating parameters of the air interface, characterized in that the means for transforming comprise a control unit with statistical logic defining rank functions (p) of the input space and output space and rules for statistical logic the transformation between the entrance and exit spaces. Adaptive air interface according to Claim 1, characterized in that the rules of the statistical logic which determine the transformation between the entrance and exit spaces take place after a further sharpening operation. Adaptive air interface according to claim 1 or 2, characterized in that the means for retrieval have the ability to obtain information about measured values, user needs, consideration towards the operator and given resources. Adaptive air interface according to claim 1, 2 or 3, characterized in that the means for transformation comprise a state machine. Adaptive air interface according to claim 4, characterized in that the control unit for statistical logic can carry out optimization of the ranking functions, where the optimization is based on a cost function (CF). Adaptive air interface according to claim 5, characterized in that the cost function is based on the rule performance> <quality h = -ï-ii: oc costs 1 spectrum use> <energy consumption cost OC Adaptive air interface according to one of the preceding claims, characterized in that the input space comprises the parameters: data rate, mobile speed, delay, distance from the base station, delay variations, remaining capacity in the base station, and bit error rate (BER). Adaptive air interface according to claim 7, characterized in that the output space comprises the parameters: frame time, modulation system, bandwidth, code speed, intermittent factor, the power of the base station and the power of the mobile station.