Measurement and carrier group based optimization in wireless OFDM multi-carrier communication systems

#The disclosed embodiments relate generally to multi-carrier wireless communication systems, and, more particularly, to scanning/measurement and report reduction in multi-carrier OFDM systems.

#In current wireless communications systems, 5 MHz˜10 MHz radio bandwidths are typically used for up to 100 Mbps peak transmission rate. Much higher peak transmission rate is required for next generation wireless systems. For example, 1 Gbps peak transmission rate is required by ITU-R for IMT-Advanced systems such as the 4th generation (“4G”) mobile communications systems. The current transmission technologies, however, are very difficult to perform 100 bps/Hz transmission spectrum efficiency. In the foreseeable next few years, only up to 15 bps/Hz transmission spectrum efficiency can be anticipated. Therefore, much wider radio bandwidths (i.e., at least 40 MHz) will be necessary for next generation wireless communications systems to achieve 1 Gbps peak transmission rate.

#Orthogonal Frequency Division Multiplexing (OFDM) is an efficient multiplexing scheme to perform high transmission rate over frequency selective channel without the disturbance from inter-carrier interference. There are two typical architectures to utilize much wider radio bandwidth for OFDM system. In a traditional OFDM system, a single radio frequency (RF) carrier is used to carry one wideband radio signal, and in a multi-carrier OFDM system, multiple RF carriers are used to carry multiple radio signals with narrower bandwidth. A multi-carrier OFDM system has various advantages as compared to a traditional OFDM system such as easier backward compatibility, better reuse on legacy single-carrier hardware design, more mobile station hardware flexibility, and lower Peak to Average Power Ratio (PAPR) for uplink transmission. Thus, multi-carrier OFDM systems have become the baseline system architecture in IEEE 802.16m (i.e. for WiMAX 2.0 system) and 3GPP Release 10 (i.e. for LTE-Advanced system) draft standards to fulfill system requirements.

#The accompanying drawings, where like numerals indicate like components, illustrate embodiments of the invention.

#FIG. 1 (Prior Art) illustrates the traditional scanning process of mobile stations and multi-carrier base stations.

#FIG. 2 illustrates a multi-carrier OFDM system in accordance with one novel aspect.

#Reference will now be made in detail to some embodiments of the invention, examples of which are illustrated in the accompanying drawings.

#FIG. 2 illustrates a wireless multi-carrier orthogonal frequency division multiplexing (OFDM) system 20 in accordance with one novel aspect. Multi-carrier OFDM system 20 comprises a plurality of base stations, and each BS supports one or multiple radio frequency (RF) carriers. For example, four contiguous RF carriers #1 to #4 are supported in OFDM system 20, BS22 and BS23 support all four RF carriers #1 to #4, BS24 and BS26 support two RF carriers #2 and #3, and BS25 supports two RF carriers #3 and #4. Each base station (e.g., BS22) comprises a common media access control (MAC) module 31, an adaptive multi-carrier controller 32, a plurality of physical layer modules PHY1-PHY4, a plurality of RF transceivers RF1-RF4 coupled to a plurality of antennas, and a multiplexer 33 that interconnects the PHY modules PHY1-PHY-4 and the RF transceivers RF1-RF4. Each PHY module, RF transceiver and antenna forms a transmission module (e.g., 29) as depicted in FIG. 2. Each transmission module corresponds to the operation of one RF carrier. Common MAC module 31 is coupled to both adaptive multi-carrier controller 32 and the transmission modules. Similarly, each mobile station (i.e., MS21) comprises a common MAC module 34, PHY modules 35-36 (PHY1-PHY2), an RF transceiver 37 coupled to antenna 38, and a multiplexer 39 that interconnects the PHY modules PHY1-PHY2 and the RF transceiver.

#In multi-carrier OFDM system 20, mobile station MS21 performs scanning (measurement) and detects preamble signals (synchronization signals) transmitted by various base stations over various RF carriers. It is noted that the terms “scanning” and “preamble signal” are defined in IEEE 802.16m WiMAX systems. In 3GPP LTE-advanced systems, on the other hand, the terms “measurement” and “synchronization signal” are defined instead, and have substantially the same meaning as the terms “scanning” and “preamble signal”. In the present application, the terms “scanning” and “measurement” are used interchangeably, and the terms “preamble signal” and “synchronization signal” are used interchangeably.