Block-Interleaved Frequency Division Multiple Access and its Application in the Uplink of Future Mobile Radio Systems
In this project, a new multiple access scheme denoted as Block-Interleaved Frequency Division Multiple Access (B-IFDMA) is presented and investigated with respect to its suitability for an application in the uplink of future mobile radio systems. For that purpose, new algorithms are presented that complement the scheme. The properties of the scheme are analyzed and compared to the properties of other well-known multiple access schemes.
At first, a new, general, digital system model is introduced that makes a joint description of B-IFDMA and various other well-known multiple access schemes that are related to B-IFDMA possible and enables a clear and proper illustration of their relations. Amongst other things, it is shown that B-IFDMA can be considered as Orthogonal Frequency Division Multiple Access (OFDMA) with pre-coding of the data and with blocks of equal size of adjacent subcarriers that are equidistantly distributed over the total available bandwidth. Further on, it is identified that B-IFDMA can be regarded as a generalization of Single Carrier Frequency Division Multiple Access (SC-FDMA).
Based on the new system model, it is shown that, in the uplink, a simple receiver structure can be applied for B-IFDMA. The simple receiver structure is based on a separation of different users’ signals in frequency domain and subsequent equalization applying frequency domain equalizers to the different users’ signals, which leads to a low computational receiver complexity.
Subsequently, different new algorithms are presented and discussed that make an efficient application of B-IFDMA in a future mobile radio system possible. In particular,
• an algorithm for B-IFDMA signal generation in time domain providing a low computational complexity,
• an algorithm for application of orthogonal and non-orthogonal Space-Time Codes to B-IFDMA providing a low computational complexity,
• an algorithm for application of Space-Division Multiple Access to B-IFDMA providing a low computational complexity, and
• an algorithm for a flexible and efficient accommodation of different data rates to the users within a mobile radio cell providing a low computational complexity and maintaining the orthogonality of different users’ signals are described.
Finally, in this project, the properties of B-IFDMA regarding
• the exploitation of diversity in frequency, time, space and among different users,
• pilot symbol overhead for channel estimation,
• robustness to carrier frequency offsets,
• power efficiency of the power amplifiers, and
• computational complexity are extensively investigated. It turns out that the properties of B-IFDMA in part strongly depend on the choice of the parameters.
As an important result of the investigation of the properties of B-IFDMA, the scheme is shown to provide a good bit error rate performance due to a good exploitation of frequency diversity for the assignment of a high number of subcarrier blocks. This performance is further improved by the application of Space Time Coding. Thus, in contrast to multiple access schemes that are focused on the adaptation of the transmission to the current channel conditions, B-IFDMA does not require any channel state information at the transmitter. Consequently, B-IFDMA is especially suited for non-adaptive transmission which is required in scenarios where channel state information at the transmitter cannot be provided, e.g., due to a high change rate of the channel conditions caused by high user mobility. It is shown that, compared to other schemes, B-IFDMA is more robust to carrier frequency offsets, provides lower pilot symbol overhead for channel estimation, provides a higher power efficiency of the power amplifier and is very flexible. Thus, it can be concluded that B-IFDMA is an interesting and well-suited candidate for the non-adaptive uplink of future mobile radio systems.