INTERLEAVE DIVISION MULTIPLE ACCESS

SAKSH SETHI 3rd YEAR ELECTRONICS

ENGG.

SEMINAR GUIDE MR. AMIT JAISAL LECTURER

CONTENT

MULTIPLE ACCESS TDMA FDMA OFDMA CDMA Problems associated with current MA schemes Interleave Division Multiple Access Mechanism of Interleaving process IDMA transmitter and receiver Types of Interleavers in IDMA scheme Advantages of IDMA scheme Comparison of Different MA Schemes Conclusion Future Aspects

MULTIPLE ACCESS

Multiple hosts sharing the same medium

Multiple access schemes to allow many users to share simultaneously a finite amount of radio spectrum resources i.e. band.

TDMA(Time Division Multiple Access)

TDMA uses different time slots for transmission and reception.

FDMA(Frequency Division Multiple Access)

In this technique the bandwidth is divided into a number of Channels and distributed among users with a finite portion of bandwidth for permanent use.

OFDMA(Orthogonal Frequency Division Multiple Access)

The spacing between carriers are such that they are orthogonal to one another.

user1

user2

user3

user4

CDMA(Code Division Multiple Access)

Users occupy the same bandwidth in same time slot, however they are all assigned separate codes.

Problems associated with current MA schemes

The demand for high data rate services increasing day by day.

Sensitivity to inter-symbol interference and frame synchronization is required in orthogonal schemes.

Though CDMA mitigates inter-symbol interference and supports asynchronous transmission, but the problem is of intra-cell interference.

CDMA is only suitable for slow-speed continuous-time transmission

In CDMA scheme rate change for one user affects whole cell-wise code-assignment plan.

Interleave Division Multiple Access

IDMA scheme relies on interleaving which means to distinguish the signal from different users.

In Interleaving mechanism the input data rearranges itself such that consecutive data bits are split among different blocks and is swapped in a known pattern amongst them.

At the receiver end, the interleaved data is arranged back into the original sequence with the help of de-interleaver.

Mechanism of Interleaving Process

IDMA Transmitter and Receiver

Types of Interleavers in IDMA scheme

Random Interleaver

Master Random Interleaver

Tree based Interleaver

Prime Interleaver

Random Interleaver

Random interleavers scramble the data of different users with different pattern. Patterns of scrambling the data of users are generated arbitrarily.

Master Random Interleaver

In master random interleavers or ‘powerinterleaver’ method, a master interleaver pattern F is assigned. Then K (K is an integer) interleavers can be generated using πk = Фk.

Ф 1 (c) = Ф (c),

Ф 2 (c) = Ф(Ф (c)),

Ф 3 (c) = Ф (Ф (Ф (c))), etc.

Tree based Interleaver

The mechanism of Tree Based user-specific interleaver generation is based on two master interleavers, which are randomly selected.

This minimizes the computational complexity and memory requirement that occur in power interleaver and random interleaver, respectively.

Prime Interleaver

Prime numbers are used as seed of interleaver. Here, user-specific seeds are assigned to different users.

The Prime Interleaver is basically aimed to minimize the bandwidth and memory requirement that occur in other available interleavers with the improvement in bit error rate (BER)performance.

Advantages of IDMA scheme IDMA scheme overcome the correlated

channel noise such as burst error or fading.

IDMA scheme has high spectral efficiency, improved performance and low receiver complexity.

Allows a very simple chip by chip iterative multiuser detection.

Comparison of different MA schemes

Parameters TDMA FDMA OFDMA CDMA IDMA

Channel scenario parameters

Time slot Frequency Orthogonal frequency

Signature sequence

Interleaver

ISI elimination

Equalization

Cyclic prefix

Cyclic prefix

Rake receiver

Iterative CBC detection

Solutions to high single user rate

High order modulation

High order modulation

High order modulation

Multi code CDMA

Variable coding rate

Intra-cell interference

N-A N-A N-A Yes Yes

Inter-symbol interference

Sensitive Sensitive Sensitive Mitigated Mitigated

Synchronization required

Yes Yes Yes No No

Conclusion

It has been observed that where CDMA was suffering from ISI and fading problems, the IDMA scheme makes the communication system immune up-to a great extent from such degradations.

Future aspects

The performance of IDMA can be further improved by the implementation of orthogonal frequency along with the IDMA.

In OFDM-IDMA, there is the addition of inverse FFT in Transmitter and FFT operation at receiver.

With the implementation of OFDM-IDMA the MUD can be realized efficiently.

References

Yi Hong, Member, IEEE, and Lars K. Rasmussen, Senior Member, IEEE, “Iterative Switched Decoding for Interleave-Division Multiple-Access Systems.”

Li Ping, Member, IEEE, Lihai Liu, Student, IEEE, Keying Wu, Student, IEEE, and W. K. Leung ,“Interleave-Division Multiple-Access.”

Li Ping, City University of Hong Kong, “Interleave-Division Multiple Access and Chip-by-Chip Iterative Multi-User Detection.”

  Manoj Kumar Shukla, Associate professor, HBTI, KANPUR,

“Performance Evaluation of IDMA Scheme in Wireless Communication.”

Thank-You