Multistage multiuser detection for FHMA

Abstract

A multistage multiuser detector (MMD) is presented for frequency hopping/code division multiple access (FH/CDMA.) The MMD reduces the bit error rate over the conventional detector by exploiting prior knowledge of the addresses and energies of the users. This detector is a conservative multiuser detector which is robust to unknown users and is only linear in complexity in the number of users. The performance analysis of the synchronous MMD (SMMD) includes both theoretical and simulation bit error rates for the noiseless case and simulation results in the presence of noise. The MMD is then extended to the asynchronous case. This asynchronous multistage multiuser detector (AMMD) is compared via simulation to the conventional detector.

Residue number system assisted fast frequency-hopped synchronous ultra-wideband spread-spectrum multiple-access: a design alternative to impulse radio

“…However, the MS/UWB FHMA system is capable of supporting more than users, if efficient MUD techniques can be employed. More explicitly, the -stage MS/UWB FHMA system using the RNS moduli and MFSK modulation can support up to number of users by invoking MUD techniques [19], [20]. If the number of users, , is higher than the number of unique FH addresses, , i.e., , then a given FH address can be assigned to a group of users and the users in this group are distinguished by their corresponding MUD address, , .…”

“…1 In our proposed system, we assume that is an integer larger than one, i.e., that FFH is employed [18]. In order to distinguish between different users, each user is assigned a user-signature FH pattern also referred to as an address code [18]- [20]. Let the address code of the th user, , be expressed as , where , , and denotes a Galois field over .…”

“…In the MUD algorithm proposed by Fiebig [19], the receiver requires the knowledge of all users' MUD addresses, as well as further side-information as to which users are active. Finally, in [20], a multistage MUD algorithm modeled after the multistage detector designed for DS-CDMA systems has been proposed, which removes the MUI by exploiting the knowledge of both the users' MUD addresses and their powers. The multistage MUD algorithm proposed in [20] can be used by both synchronous and asynchronous fast FHMA systems and it was argued that this multiuser detector has a linearly increasing complexity as a function of the number of active users.…”

“…In the previous section, we illustrated that when a conventional SUD is considered, the first user's symbol of 1 might be erroneously detected as symbol 2, since both row one and row two have three entries. However, based on the MUD algorithms developed in [19] and [20], the MUI inflicted upon the first user's signal by user 2 and 3 can be canceled by jointly exploiting the information of all three users. Specifically, since both the decoded time-frequency matrices and of Fig.…”

“…Another reason of using the synchronous assumption is that the transmitted narrowband signals in MS/UWB FHMA systems usually only experience flat-fading and in this scenario accurate synchronization can be readily achieved. We will demonstrate that synchronous MS/UWB FHMA constitutes a high-efficiency multiple access scheme capable of supporting an extremely high number of users with the aid of relatively simple receivers, which have been previously proposed in the literature [18]- [20].…”