The present invention relates to communication of data and in particular to modulation of data transmitted between two entities of a communication system.
A communication system is a facility which facilitates communication between two or more entities such as communication devices, network entities and other nodes. A communication system may be provided by one more interconnect networks. It is noted that although a communication system typically comprises at least one communication network, for example a fixed line network or a wireless or mobile network, in its simplest form a communication system is provided by two entities communicating with each other. The communication may comprise, for example, communication of data for carrying communications such as voice, electronic mail (email), text message, multimedia and so on.
A user may communicate by an appropriate communication device. An appropriate access system allows the communication device to access to a communication system. An access to the communications system may be provided by a fixed line or wireless communication interface, or a combination of these. Examples of wireless access systems include cellular access networks, various wireless local area networks (WLANs), wireless personal area networks (WPANs), satellite based communication systems and various combinations of these.
A communication system typically operates in accordance with a standard and/or a set of specifications and protocols which set out what the various elements of the system are permitted to do and how that should be achieved. For example, it is typically defined if the user, or more precisely user device, is provided with a circuit switched bearer or a packet switched bearer, or both. Also, the manner in which communication and various aspects thereof should be implemented between the user device and the various elements of the communication and their functions and responsibilities are typically defined by a predefined communication protocol.
In a radio or wireless system an entity in the form of a base station provides a node for communication with user communication devices, often referred to as mobile stations. Communications in the direction from the base station to the user device is seen as occurring on a “downlink” (DL). Communications in the direction from the user device to the base station is then seen as occurring on an “uplink” (UL). It is noted that in certain systems a base station is called ‘Node B’.
Signalling between various entities may be divided between signalling of control data and actual data. The latter refers to the data content the users wish to communicate. Control signalling, in turn, associates to transfer of information that is not related as such to the data content the users may wish to be transferred. In the following these two forms of signalling are separated by referring to control signalling and data signalling, where appropriate.
To ensure proper operation of the system, the control signalling typically has higher quality requirements than the data signalling. On the other hand, the amount of information conveyed by control signalling such as by acknowledgement signalling is typically only one or two bits. This is less than what can be carried by data modulated symbols, for example Quadrature amplitude modulated (QAM) symbols. For example 16QAM carries 4 bits and 64 QAM carries 6 bits.
An example of control signalling is the transfer of positive and negative acknowledgement information signalling, often referred to as ACK/NACK signalling. The acknowledgement signalling is used to provide feedback concerning previous transmissions, for example if a previous data transmission such as a data packet is properly received.
Despite the advantages in signalling technologies, there is still need to optimize the performance of communications between two devices, for example though reduction of errors in control signalling. Use of a single modulation method for control signalling and data signalling might be desired in various applications.
The herein described embodiments aim to address one or several of the above mentioned shortcomings and/or desires.