Networks that include a number of access technologies means that a user device or a user-network—which comprises a number of devices, such as a laptop with a WLAN access card and Bluetooth or an inter-connected personal area network—can connect via one or more radio access technologies to a peer node. These access technologies can be provided by a single network operator, or alternatively by a number of network operators. Examples, are the 3GPP mobile networks that provide mechanisms and reference points for integrating a number of access technologies (GSM, (E)GPRS, enhanced EDGE, UMTS, HSPA, evolved HSPA, LTE, WLAN, WiMAX, and others).
Within a multi-access system as described above, there is a problem caused by frequency interference between different radio technologies. In particular, within an end system (user device or user-network), there can be substantial interference between radio transceivers of different access technologies.
To some extent this problem has been addressed in order to coordinate the usage of WLAN and Bluetooth in wireless devices. Since both WLAN and Bluetooth networks operate in the same frequency band, the coordinated use (e.g. time shared usage of WLAN and Bluetooth) can reduce interference. However, a first requirement is to determine which access interferes with what other access. In case of WLAN and Bluetooth the mutual interference is already known due to the fixed allocation of both access technologies to the same frequency band. In the future, this a-priori knowledge about the inter-interference between different access technologies cannot be assumed.
Radio access technologies are increasingly decoupled from frequency bands (i.e., technology-neutral frequency allocation). While GSM and UMTS today have fixed frequency allocations, LTE and WiMAX are standardized to be applicable in any frequency band of different bandwidths. Also a re-use of 2G frequency bands or TV frequency bands for any 3G/4G technologies is being considered. In the context of cognitive radio (as, for example, standardized in IEEE 802.22 or IEEE P1900) a flexible allocation of a radio technology in any frequency band is being investigated. It can be expected that sooner or later many access technologies can be used in several different frequency bands.
User-networks or user devices use an increasing number of radio transceivers. Such radio transceivers utilize, for example, Bluetooth, WLAN, GSM/EGPRS, UMTS/HSPA, LTE, WiMAX, ZigBee, DVB-H/M, DAB, etc. Note that it is not required that every access technology have a dedicated modem. It can also be that the user-network has a number of configurable modems (software-defined or software-reconfigurable radio) that can be configured for different access technologies.
Users become increasingly independent from network providers, e.g. by having multiple subscriptions or more dynamic agreements with access providers, or by regulatory open access schemes that require an operator to provide service to any user. As a result, they can connect to different access providers providing different types of access in different frequency bands. In this multi-actor scenario, a single access provider is not automatically coordinating the inter-system interference by according frequency spacing. Instead, it can be that two access providers provide access (based on the same or different technologies) in close frequency bands, such that the simultaneous usage of the two access systems causes interference between the access systems in the user-network.
U.S. Pat. No. 7,117,008 addresses the problem of cross interference among multiple radio frequency devices in a wireless communication-enabled computer system. Mitigating cross interference is purportedly accomplished by selectively blocking a particular signal. Priority is assigned to each active transceiver and based on priority and pending transactions, control of the communications is arbitrated between active wireless transceivers.