Patent Application
20130215867
This application claims priority to Spanish Application Number 201230257, filed on Feb. 20, 2012, the entirety of which is incorporated herein by reference.
The invention relates to mobile communication networks, especially to a system and a method for managing traffic in a mobile communication network. It also relates to a computer program product comprising instructions needed for performing said method.
In mobile communication systems resources are restricted: resources such as bandwidth, frequencies, time slots (i.e. short time windows) and codes which are shared by a plurality of terminals, either mobile or static, are all limited to some degree.
GSM is one of the most successful mobile telecommunications network technologies. Even in mature markets where other network technologies, for example UMTS, are widely spread, the majority of voice traffic is still handled by GSM networks, mainly due to its better coverage.
However, this scenario is already changing and will significantly change in the future due to the main following facts:
The above facts imply a gradual decrease of traffic load in GSM networks ending up in a medium/long term scenario where low or even zero voice traffic will be handled by GSM Networks, while GSM data traffic contributor will be mainly M2M services. Since these services normally entail long term (e.g. beyond 2020) contracts between the operator and the customer, operators will be obliged to keep their GSM Networks active, at least, to cope with M2M services. The resulting traffic will consist of low load and very scattered and intermittent traffic profile.
However, traditional GSM Networks are designed to carry voice services under mobility scenarios and significant traffic loads. In GSM, the communication between a mobile terminal and a serving cell belonging to a base transceiver station or base station provides the mobile terminal with a radio frequency channel and all the mobile terminals attached to a same base transceiver station make use of the same frequency channels assigned to said base station. The provided radio frequency channel has a TDMA frame with eight time slots.
In terms of spectrum resources, GSM networks show two frequency layers:
At least one BCCH layer and its related frequency, is allocated to each cell. A TCH layer is also commonly used and provides capacity on top of the BCCH layer. But this kind of structure is not prepared to adapt resources utilization to scenarios of very low and scattered traffic, being quite inefficient due to the following main facts:
This means that a significant piece of the available spectrum plus high consumption of power resources would be unnecessarily used for the medium/long term traffic profile described above.
A GSM based solution that can handle these targeted scenarios by allocation of a small piece of spectrum and by not requiring continuous transmission is not currently known.
This invention addresses the previously mentioned drawbacks by adapting the network traffic management functionality.
In the following discussion, it is assumed that the TCH layer can be removed entirely, since extra capacity is not needed for the traffic profile described above.
An object of the present invention is to provide a system and a method for managing traffic in a mobile communication network, reducing the capacity needs with respect to the radio spectrum and enhancing the efficiency of the use of the radio resources where traffic in a certain area is self managed in terms of spectrum and power resource allocation.
The system of the invention comprises a first base station and at least a second base station and it is operative for providing a communication between a terminal and any of the base stations, which provides said terminal with a radio frequency channel having an assigned timeframe structure comprising a plurality of time slots.
Moreover, the object of the invention is achieved by the first base station and the second base station comprising their respective time slots synchronised and being both configured to provide the same radio frequency channel, said channel comprising:
Advantageously the system prevents the continuous radiation of power due to allocation, for each base station, of the logical Broadcast Control Channel to at least one time slot of the shared radio frequency channel. This means that every base station does not continuously transmit the pilot because it only does so during its corresponding time slot which results in a power consumption decrease and interference reduction, so another further advantage of the present invention is avoiding interference which diminishes the signal received by the mobile terminal or the base station.
Other time slots where logical Broadcast Control Channel (BCCH) have not been configured are used as a pool or shared time slots of resources for voice and data traffic (TCH) handling, so it is possible that radio spectrum capacities are dynamically shared between a plurality of base stations.
Advantageously the system may enable low spectrum utilization, for example, from 0.2 MHz in an extreme case to 1 MHz depending on traffic needs and to offer such radio spectrum capacity for mobile radio network functionality according to future needs. This means that a more efficient utilization of the infrastructure of mobile radio networks is possible, especially in those situations where low and scattered traffic occurs.
The shared time slots of the radio frequency channel may be used in a communication process with any of the base stations and only for one base station at any time, but in a first point of time any of these shared time slots can be used for a communication with the first base station and, when the first communication has been released, in a second point of time for another communication with the second base station.
In accordance with a further aspect of the invention there is provided a method for managing traffic in said described system of a mobile communication network, the method comprising the following steps performed in a first base station:
In accordance with a yet another aspect of the invention there is provided a computer readable program code executable by a data processing system and configured to perform said method.
To complete the description and in order to provide for a better understanding of the invention, a set of drawings is provided. Said drawings form an integral part of the description and illustrate a preferred embodiment of the invention. The drawings comprise the following figures:
The cell to which a terminal (MT1, MT2) is attached is called a serving cell. Each cell uses a channel to receive a corresponding signal, a channel is to be understood as a radio frequency range during a specific time (time slot).
As shown in
In the shown example, the method comprises the step of providing the mobile terminal (MT1) one of said shared time slots (TS1, TS3, TS5 to TS7) taking also into account that the allocated time slot (TS) has not been previously allocated by one of the base stations (BTS1, BTS2, BTS3) to another terminal (MT2). If time slot 1 (TS1) was previously allocated to a second terminal (MT2) by the second base station (BTS2), the available time slots would be (TS3, TS5 to TS7). That means that the method also comprises steps for sharing information among the base stations (BTS).
The shared information, ie, available time slots (TS), can be handled by a centralised controller, for example, a base station controller (BSC) or responsibility can be decentralized across the base stations (BTS) for example through interfaces that interconnects the base stations (BTS), in a way that all base stations (BTS) are real time aware of the resources, ie, channels and frequencies, used by their neighbouring base stations (BTS). In this case each base station (BTS) is self managed and it exchanges information with the other base stations (BTS).
The method of the invention further comprises the step of setting the first base station (BTS1) for sending the information relating to the allocated time slot (TS3) and, if required, the step of sending the information relating to the released time slot (TS3) once the call is over.
In order to better understand the invention an example of a call assignment under the one frequency channel (f1) extreme scenario, in case that every base station (BTS) is real time aware of resources utilization by the others base stations (BTS), is included:
One way of considering the mechanism described above is that of a “pooling” mechanism. For example, when a time slot of the shared time slots is allocated to a terminal/base station pair, this time slot cannot be used by other terminal/base station pairs until the call is released and this time slot has become available for re-allocation. Therefore, a time slot of the shared time slots would be used alternatively by different terminal/base station pairs. However, this alternative use would not be in a periodic or planned manner, but on a first-come-first-served basis (i.e., as a pool). In other words, a time slot of the shared time slots is “pooled” between different terminal/base station pairs. In an alternative scenario, the time slot of the shared time slots might be assigned to a specific terminal/base station pair for (i) a period of one or more frames or (ii) until the call is released, whichever is earlier.
Some of the advantages of the present invention are:
(a) the ability to provide GSM service over the smallest possible portion of spectrum: just a mere 200 KHz. Currently, in order to provide GSM service with acceptable performance, around 4,4 MHz are required—namely 22 times over the spectrum required by a mechanism implemented according to the present invention;
(b) the power consumption of the system would be reduced to a fraction (at least ⅛) of the power consumption of a standard GSM system with only BCCH carriers used;
(c) a mechanism implemented in accordance with the present invention would be totally transparent for the terminals, that is, compatible with any legacy GSM terminal. Thus, GSM service does not need to be discontinued or altered;
(d) it can be implemented over legacy Base Stations/Controllers just through software upgrade, i.e. it will not require further modifications and/or investments in GSM hardware. Therefore, a mechanism implemented in accordance with the present invention would enable smooth adaptation of GSM systems to an expected traffic decline, moving from a voice-centric network to a “M2M”-centric one in a transparent way for the users of the network.
Although an embodiment of the invention has been described above, further applications of, and modifications to, the present invention will be readily apparent to the appropriately skilled person from the teaching herein without departing from the scope of the appended claims. For example, a “terminal/base station pair” might include an arrangement whereby a terminal is served by one or more base stations.
| Number | Date | Country | Kind |
|---|---|---|---|
| 201230257 | Feb 2012 | ES | national |
