Clark School Home UMD

ISR News Story

Source Encoding Assisted Multiple Access (SEAMA) Protocol for Voice-Data Integrated Wireless Networks: A Technique for Trading Quality of Service for Network Capacity (ISR IP)

ISR intellectual property available to license

Mehdi Alasti, Nariman Farvardin

Some recently proposed Multi-Access Protocols (MACs) integrate voice and data in wireless communication networks; Packet Reservation Multiple Access (PRMA) is one such protocol proposed for micro-cellular wireless communication systems. In PRMA, voice and data are separated. The bandwidth is dynamically partitioned between voice and data, i.e., unused voice slots are assigned to data traffic. In order to increase the bandwidth assigned to data, in PRMA

a call in silence mode gives up accessing the channel. During a talk period, however, PRMA assigns a fixed bandwidth to the call. PRMA does not take into account the variations of the speech signal within the talk period; this leads to bandwidth inefficiency.

PRMA++ is a variation of the PRMA protocol where mobile units contend to notify their bandwidth requirement via request packets and dedicated bandwidth. This arrangement retains the inefficiency of PRMA.

ETDMA, a Time Division Multiple Access (TDMA) out of slot scheme was introduced by Hughes Network Systems. In this system mobiles are not assigned time slots for the duration of the call but are dynamically assigned slots in full-duplex RF channels. Each channel contains six half-rate slots so that for a twelve channel group there are 72 slots of which 63 are assigned to talk and 9 are reserved for data.

There are also proposals for 3rd Generation wireless systems, e.g. Enhanced Data Rates for Global Evaluation (EDGE) (AT&T and Lucent Technology), that employ PRMA or a variation of it in the MAC protocol.

The protocols and schemes identified above do not fully exploit the characteristics of the voice encoder, e.g. they do not take into consideration variations in speech or compression techniques. By employing an appropriate voice encoder and exploiting its characteristics, e.g. time variations of the speech coding rate and embeddedness of the vocoder output, researchers (including an inventor of an important component of the V-34 modem protocol) at the University of Maryland, College Park, have developed a source encoding assisted access protocol that increases capacity of an integrated voice-data system in a circuit switched network by 100% and by between 40% to 50% without a perceived drop in the quality of the voice transmission relative to packet-switched protocols.

For more information
If you would like to license this intellectual property, have questions, would like to contact the inventors, or need more information, contact ISR External Relations Director Jeff Coriale at or 301.405.6604.

Find more ISR IP
You can go to our categorical IP search page to search by research category or faculty name. Or view the entire list of available IP on our main IP search page.

ISR-IP-Farvardin ISR-IP-wireless-networks ISR-IP-protocols

Related Articles:
Congestion Control in Satellite Networks (ISR IP)
Method for Efficient Source Authentication for Multicast Communications in Hybrid Satellite/Wireless Networks (ISR IP)
Method for Performance-Aware Security of Unicast Communications in Hybrid Satellite Networks (ISR IP)
A New Method of Matrix Spectral Factorization with Applications, Including, but not Limited to, Data Compression, Filtering, Wireless Communications, and Radar Systems (ISR IP)
Method and Implementation for Wireless Message Authentication (ISR IP)
FICA: Low Profile F-Inverted Compact Antenna (ISR IP)
Method and Apparatus for Bandwidth-Constrained Queries in Sensor Networks (ISR IP)
A Practical Method for Resource Allocation for QoS in OFDMA Wireless Systems (ISR IP)
Rapid Specific Absorption Rate (SAR) Assessment System (ISR-IP)
A Data-Bearing Approach for Pilot-Embedding in Space-Time Coded MIMO Systems (ISR IP)

June 18, 2007

Prev   Next



For more information, contact ISR External Relations Director
Jeff Coriale at or 301.405.6604.

Current Headlines

University of Maryland Launches Quantum Technology Center

Min Wu named Associate Dean for Graduate Programs

Mapping Nucleation Kinetics with Nanometer Resolution

MEI² Receives Two New Innovative Vehicle Technology Awards

New EventAction interface improves recommender systems

BIOE, UMB to Host October Symposium

Khaligh elevated to Fellow of Institution of Engineering and Technology

Alumnus Amir Ali Ahmadi receives PECASE Award

Alum Samuel Gollob is NSF Graduate Research Fellow

Espy-Wilson, Sivaraman research aims to improve speech inversion

News Resources

Return to Newsroom

Search News

Archived News

Events Resources

Events Calendar