Telecommunications – Radiotelephone system – Zoned or cellular telephone system
Reexamination Certificate
1998-09-15
2001-09-11
Chang, Vivian (Department: 2682)
Telecommunications
Radiotelephone system
Zoned or cellular telephone system
C455S436000, C455S522000, C370S252000
Reexamination Certificate
active
06289217
ABSTRACT:
TECHNICAL FIELD
The invention relates generally to adapting a radio connection to the amount of data to be transmitted and to the prevailing radio traffic environment. In particular, the invention relates to such an adaptation that may take place both in the beginning and during the radio connection.
BACKGROUND OF THE INVENTION
Second-generation cellular radio systems, such as D-AMPS (Digital Advanced Mobile Phone Service), GSM (Global System for Mobile telecommunications) and PDC (Personal Digital Cellular), are mainly meant for such telephone connections that all have the same data transmission rate. In addition to telephone connections, in the future there will be made many different connections over the radio interface, such as real-time and non-real-time data transmission connections and video calls The required data transmission rate can vary largely between the different connections, and it may even change during the communication. Moreover, the interference that variably occurs in the radio connection may require coding on different levels in order to transmit the information carried in the connection to the receiver in a feasible form.
In systems based on TDMA (Time Division Multiple Access), a given time slot is allocated for the use of each single connection, the time slot being part of a cyclically repeated frame structure at a given carrier wave frequency. In systems based on CDMA (Code Division Multiple Access), the corresponding basic unit allocated for the use of a connection is a given division code within a given carrier wave frequency. In their original form, second-generation cellular radio systems do not allow the allocation of more than one basic unit for one connection at a time, but in order to make the distribution of data transmission capacity more flexible, various different suggestions have been made as to how more division codes, frame time slots or carrier wave frequencies could be allocated for a high-capacity connection. In addition to circuit-switched telephone connections, there are suggested methods and systems for creating packet-switched data communication. A packet-switched connection is easily adapted to variations in the quantity of transmittable data, because the number of packets to be transmitted per time unit depends on the quantity of data to be transmitted at each point of time and on the available data transmission capacity.
In radio communication, the nature of interference is fading or noise. In order to compensate said interference, cellular radio systems generally use adjusting of the transmission power, so that the transmitting device by some method defines the lowest possible power by which the transmitted signal is received as sufficiently strong from the point of view of the receiving device. For compensating interference, there also is sometimes used frequency hopping, i.e. rapid variation of the transmission and reception frequencies. In order to enable the receiver to interpret the signal correctly in spite of interference, the transmitter may interleave and code the signal prior to transmitting.
All such measures that aim at maximising the quality of the radio connection and the effective use of resources and at the same time at minimising the power consumption caused by transmission and reception can together be called adapting of the radio link. In a third-generation cellular radio system, the frame structure of the radio interface will be considerably more complex than in current systems, which fact sets remarkably increased requirements to the adapting of the radio link. As an example of a third generation frame structure, let us study a frame structure that was introduced in the Finnish patent application No. 964,308 and in the corresponding U.S. patent application Ser. No. 802,645, filed on Feb. 19th, 1997. Each frame is divided into a predetermined number of time slots. Each time slot can be further divided either into smaller time slots or sections of the size of one division code or one narrow frequency band. Time slots and parts of them, divided in some other fashion, can together be called slots. Time slots can be divided into slots in different ways, so that one frame may contain slots of varying sizes. The part with the smallest data transmission capacity contained by the frame, which part as a whole can be allocated for the use of one data transmission connection, is called a resource unit. In separate cells, the frame structure can be divided into slots of various sizes by various different methods.
The requirements set for the adaptation of the radio link depend either on an increase or decrease in the interference level or on fluctuations in the quantity of source data to be transmitted. If the general interference level rises due to other simultaneous radio transmissions or when the propagation conditions of the radio waves on the path between the transmitter and the receiver change, the quality of the radio connection weakens. By adapting the radio link, the quality of the radio connection is attempted to be maintained above a given minimum limit. The quality of the connection is described for instance by the Bit Error Ratio (BER), the Frame Error Ratio (FER), the data transmission delay and/or the number of erroneous received bursts as compared to the number of all received bursts. If the quantity of the source data varies in time, the adapting of the radio link must aim at a situation where all source data is transmitted to the receiver within a given maximum delay. On the other hand, the data transmission capacity of the radio interface must not be kept reserved in vain for any single connection, when the quantity of transmitted data is decreased.
SUMMARY OF THE INVENTION
The object of the present invention is to introduce a method and system whereby a radio link in a third-generation cellular radio system can be adapted to varying interference circumstances and to a varying quantity of source data.
The objects of the invention are achieved by a method which combines the adjusting of the transmission power and a dynamic variation of the data transmission capacity reserved for a given connection. The latter feature is based on measuring the connection quality.
The method according to the invention is designed for adapting a radio connection to an environment changing over said connection in a cellular radio system where the radio traffic between the base station and the mobile stations is arranged on a multiple function principle according to a given frame structure. In said method, form a given connection between a transmitting and a receiving device, there is reserved a given data transmission capacity of said frame structure. The method according to the invention is characterised in that during the connection, the receiving device measures the connection quality, and on the basis of the measured connection quality, the data transmission capacity reserved for said connection in said frame structure is changed.
Most advantageously the invention is applied in a third-generation cellular radio system, where the concept ‘bearer’ is used for describing the connection between the base station and the mobile station. Here bearer means the entity formed by all such factors that affect the data transmission between the base station and a given mobile station. The concept bearer includes, among others, data transmission rate, delay, bit error ratio and fluctuations in these within given minimum and maximum values.
The bearer can also be understood as a data transmission path created due to the combined effect of all these factors, said path connecting the base station and a given mobile station, through which path it is possible to transmit useful data, i.e. payload information. One bearer always connects only one mobile station to the base station. Multiple function mobile stations can simultaneously maintain several bearers that combine the mobile station to one or several base stations.
In connection with the bearer setup, there are selected values for certain basic parameters, and among the factors af
Hamalainen Seppo
Laaksonen Niina
Lappeteläinen Antti
Salonaho Oscar
Appiah Charles N.
Chang Vivian
Nokia Mobile Phones Ltd.
Perman & Green LLP
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