OPNET Research and Educational Projects
Sponsoring Professor: Harsha R. Sirisena
Research Assistants: Shehan Perera, William Liu, A. Jayananthan, Feng Deng
We are using OPNET for:
1. Qos management for two coexisting systems: IEEE802.16/3G and IEEE802.16/IEEE802.11e
Lately a number of technologies have been investigated to provide the efficient networking traffic management. Examples as Quality of service management functions in UMTS, service differentiation introduced in the hot last-mile techniques named 802.16 for WMAN and 802.11e for WLAN. The project aims to explore the role of all of these techniques on QoS solutions taking both implementations and performance into consideration.
Based on the primary analysis on MAC layer, the research will be developed considering quality of service for the interworking UMTS/802.16 and 802.16/802.11e networks, where 802.16 will provide the backhaul for the remote 3G base stations and 802.11e wireless LAN. A bonus-outcome has the potential to combine these three different systems together, achieving a more complicated network. A successful outcome will accelerate the deployment of future wireless communication environments taking the benefits from UMTS, IEEE802.16 and 802.11e with a substantial improvement in the traffic management.
Some research work are currently undergoing within the area of constructing hybrid wireless network. This project work is therefore on the WMAN/3G and WMAN/WLAN coexisting issues.
- For WMAN/3G system, IEEE802.16 acts as the RNC (radio network controller) in this UTRAN system.
- For WMAN/802.11e system, IEEE802.16 also works as the backhaul for the WLAN communications.
- Further consideration is to build an overall wireless system deploying all of those technologies where IEEE802.16 works as backhaul for 3G base-stations and WLAN interworking with 3G by loose coupling or tight coupling.
Such hybrid networks combine the strengths of cellular and advanced wireless technologies, resulting in a system capable of providing users with ubiquitous data coverage with enhanced high-speed services. The multi-domain QoS management should be consistent and could be assorted by carrying out the translation between representations of QoS at different system levels, which is also named QoS parameters mapping.
2. Mobile Broadband Wireless Access (MBWA)
Mobile broadband wireless access (MBWA) networks of the future should be able support mobile users traveling at speeds as great as 250 km/hr and be comparable to wired broadband systems, such as cable and DSL connections. This will seek to boost real-time data transmission rates in wireless metropolitan area networks from the dial-up rates of today's cellular phones to a broadband experience of 1 Mbps or more, operating in licensed bands below 3.5 GHz and optimized for IP-data transport. By providing ubiquitous mobile broadband networking based on cell ranges of up to 15 km or more, the standard will remove barriers for mobile interactive voice, video and data services. The technology will target sustained spectral efficiencies of more than 1 bit/second/Hz/cell, which is more than double that of today's systems. It will promote fully QoS-enabled airlinks having high spectral efficiency and low latency, giving users a high-speed wireless data experience equivalent in quality to wired links.
Research Objectives
- Firstly a system model for MBWA must be created. NS2 was selected as the primary simulation package but has proved to be hard to adapt. Not many researchers have had success in this endeavour so far. Therefore, we build system model by Opnet.
- The various MAC protocols which can be used with the OFDM interface need to be investigated and modified for optimum throughput and performance.
- QoS mechanisms for mobile systems as well mappings between technologies must be devised.
- Performance of TCP over wireless OFDM links needs to be quantified and the OFDM links modeled.
- Designing a QoS aware, fair, efficient MAC protocol and simulating its performance in Opnet.
3. Next Generation Networks (NGNs) Resilience Research
Sophisticated methodologies exist for the modeling of resilience in traditional telecommunication technologies such as the public switched telephone networks and data transmission networks. In the case of Next Generation Networks (NGNs), which will use the Internet Protocol as the main mechanism for delivery of applications and services, the modeling methodologies are much less developed, mainly because an inherent complexity of these networks. Multi Protocol Label Switching with Traffic Engineering(MPLS-TE) is proposed to be deployed widely in core network of NGN. This assists in adding capabilities of Service Resilience combined with TE (Traffic Engineering), Qos (Quality of Service) and VPN (Virtual Private Network) to today’s IP networks. Our research group wants to clarify resilience issues of NGN, which is deployed with MPLS-TE in its core network and have identified OPNET as a promising tool for this purpose.
We will use OPNET to set up MPLS elements (LER, LSR, LSP) , parameters (FECs) and related attributes like traffic engineering in the core network. MPLS-TE is armed with traffic engineering and multiple protection and restoration schemes, which provide reliability in failure conditions and their repair coverage that may comprise nodes and links as well as full paths from two perspectives:
- MPLS recovery mechanisms, crucial internal components of VoIP service availability practices. The resiliency evaluation requires an accurate performance analysis based on routing protocols such as OSPF or IS-IS. Furthermore, we will develop extensions to enhance routing performance in MPLS enabled network.
- MPLS signaling protocol, a simplified version of Constrained-based Routing over Label Distribution Protocol (CR-LDP) and RSVP protocols could be researched in failure/recovery conditions with different factors accounted such as topology factors and traffic distribution.
Additionally, we expect to extend our research on GMPLS, which has been developed by the IETF to extend the classical IP MPLS standard to address the provisioning of paths at the fiber, wavelength and SONET/SDH levels of the core network.
4. TCP Enhancement Over Wireless Networks
TCP optimization for wireless networks to deal with packet losses due to fading, shadowing and contentions should preferably maintain TCP end-to-end semantics with minimal dependence on intermediate nodes. The development of wireless technologies, such as WLAN and advanced 3G networks and services, make it necessary to find a way of improving TCP’s efficiency and resource utilization. Several schemes proposed to alleviate this issue suggest that TCP needs radio network feedback mechanism to minimize the wireless environment effects by distinguishing non-congestion related losses from congestion related losses. This project investigates TCP performance over WLAN and UMTS networks using OPNET as the simulation tool.
WLANs, based on the IEEE 802.11 standard, support flexible portable and mobile computing. It supports sevral modulation schemes such as DBPSK, DQPSK, complementary code keying (CCK)and OFDM. The 802.11 protocol covers the MAC and physical layers, the standard currently defines a single MAC that interacts with different wireless transmission technologies in the Instrument Scientific and Medical (ISM) frequency bands. Distributed coordination function (DCF) is the basic access mechanism of IEEE 802.11b and uses a carrier sense multiple access with collision avoidance (CSMA/CA) algorithm to mediate the access to the shared wireless medium. In addition to the standard functionality usually performed by MAC layers, the 802.11 MAC performs additional functions such as positive acknowledgement, packet retransmission and fragmentation.
Third Generation (3G) technology is intended to revolutionize the capabilities of mobile communications and is becoming a reality. 3G mobile is expected to provide more enhanced services than are possible over existing cellular systems, including higher bit error rates services and greater capacity and service capability. Universal Mobile Telecommunications System (UMTS) is a 3G wireless protocol that is a part of the international Telecommunication Union’s IMT-2000 vision of a global family of 3G mobile communications, offering data rates up to 2Mbps. UMTS uses Wideband Code Division Multiple Access (WCDMA) to carry the radio transmissions. WCDMA uses direct spread spectrum with a chip rate of 3.84 Mcps and employs a 5MHz channel bandwidth (BW). A Node-B can support Frequency Division Duplex mode (FDD), Time Division Duplex mode (TDD) or dual-mode operation. In FDD mode, the uplink (from Node-B to mobiles), and the downlink (from mobiles to Node-B) are on different frequencies. Spreading factors vary from 256 to 4 for an FDD uplink and from 512 to 4 for an FDD downlink.
We propose a scheme that monitors the radio interface and notifies the TCP sender of any effects caused by the wireless link. The TCP end-to-end semantic is maintained but it is modified in order to adapt to the characteristics of the wireless environment. It is decided to use the OPNET for this study because
- it supports the WLAN, UMTS and other wireless networking models
- it is a well-designed and reliable networking tool that parallels the real-time network implementations
- given the standard models and guides, it helps to gain knowledge in all aspects of networking
- technical supportis available