er of uplink subframes, reception of several downlink subframes may need to be acknowledged in a single uplink subframe. The 3GPP LTE provides two mechanisms to perform this function, either through bundling or multiplexing. The network determines which mechanism to use on a per UE basis. In any case, the amount of control channel resources in an uplink subframe increases with the increasing number of downlink subframes to be acknowledged [14]. The bundling mechanism combines the acknowledgements from multiple HARQ processes such that a positive acknowledge- ment will be sent only in the case where all downlink transmissions were correctly received. The advantage of this approach is that the number of acknowledgements from a UE in single subframe is minimized, which is important especially for coverage-limited terminals. When the UE cannot detect one or several downlink assignments, to avoid erroneously positive acknowledgements, and if data in the detected subframes is correctly decoded, there is an index included in the downlink assignment where the terminal can learn how many subframes have been assigned, and hence detect whether assignments have been missed. With multiplexing, the acknowledgements from multiple HARQ processes are explicitly trans- mitted in an uplink subframe. This provides more detailed information about the decoding results of the different downlink transmissions, but requires a higher signal-to-noise ratio at the base station which may hence not be suitable for coverage-limited terminals. For uplink data transfers, the TABLE 7-2 3GPP LTE Uplink HARQ Operation [9] HARQ Feedback (UE Side) PDCCH (UE Side) UE Behavior ACK or NACK New transmission New transmission according to PDCCH ACK or NACK Re-transmission Re-transmission according to PDCCH (adaptive re-transmission) No (re)transmission, retain data in HARQ buffer and a PDCCH is required to resume re-transmissions Non-adaptive re-transmission 7.4 3GPP LTE radio link control and medium access control sub-layers individual feedback is availab