LTE, LTE-Advanced and WiMAX: Towards IMT-Advanced Networks

Intersystem Interference

Intersystem interference is the induced unwanted power in a communication system made by other communication systems using the same frequency band(s). Nowadays, advanced communication devices can be equipped with more than one radio access interface to allow it to connect to a number of access technologies. Examples of these access technologies are GSM, (E)GPRS, enhanced EDGE, UMTS, HSPA, evolved HSPA, LTE, WiFI, and WiMAX. While multi-technology handsets enable an opportunistic, user-centric service access, this enabled feature comes at the price of frequency interference that mainly occur at the mobile handset. In a multi-access system, the user device may undergo or cause substantial interference between radio transceivers of different access technologies. Intersystem interference can be alleviated, even mitigated, if a priori knowledge is available about the specific access technologies operating in a shared area, in addition to the bands that they utilize. A difficulty emerges, however, in that such a priori knowledge implies fixed frequency allocation, as is common with 2G/3G technologies. LTE and LTE-Advanced, however, have been empowered with greater flexibility in having a large number of radio spectrum allocations and for both duplexing types (FDD and TDD). This flexibility renders achieving a prior knowledge about the exact LTE spectrum bands too difficult. The emerging usage of cognitive radios introduces another source of uncertainty as to ...