Cross-layer optimization

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Cross-layer optimization is an escape from the pure waterfall-like concept of the OSI communications model with virtually strict boundaries between layers. The cross layer approach transports feedback dynamically via the layer boundaries to enable the compensation for overload, latency or other mismatch of requirements and resources by any control input to another layer, but that layer directly affected by the detected deficiency. [1] [2] [ clarification needed ]

Contents

Strict boundaries between layers are enforced in the original OSI networking model, where data is kept strictly within a given layer. Cross‑layer optimization removes such strict boundaries to allow communication between layers by permitting one layer to access the data of another layer to exchange information and enable interaction. For example, having knowledge of the current physical state will help a channel allocation scheme or automatic repeat request (ARQ) strategy at the MAC layer in optimizing tradeoffs and achieving throughput maximization. [3] [ clarification needed ]

Especially in information routing with concurrent demand for limited capacity of channels there may be a need for a concept of intervention to balance between e.g. the needs of intelligible speech transmission and of sufficiently dynamic control commands. Any fixed allocation of resources will lead to a mismatch under special conditions of operations.[ clarification needed ] Any highly dynamic change of resource allocation might affect the intelligibility of voice or the steadiness of videos. However, as with other optimizing strategies, the algorithm consumes time as well. [4]

Principles

There are principles that a cross-layer design must adhere to:

Unlike a traditional architectural design approach, where designers can focus on a single problem without worrying about the rest of the protocol stack, one must be careful to prevent unintended effects on other parts of the system. Dependency graphs are helpful for adaptation loops that occur using cross-layer design. [5]

Applications

Cross-layer optimization can be used for

Its advantages include high adaptivity in a Wireless sensor network and a larger optimization space. [5]

Adjusting quality of service

Cross-layer optimization shall contribute to an improvement of quality of services under various operational conditions. Such adaptive quality of service management is currently subject of various patent applications, as e.g. [8] The cross-layer control mechanism provides a feedback on concurrent quality information for the adaptive setting of control parameters. The control scheme apply

Tailoring to resource efficiency of cross-layer

The quality aspect is not the only approach to tailor the cross-layer optimization strategy. The control adjusted to availability of limited resources is the first mandatory step to achieve at least a minimum level of quality. Respective studies have been performed and will continue. [9]

Adapting MAC scheduling based on PHY parameters

Communication systems that need to operate over media with non stationary background noise and interference may benefit from having a close coordination between the MAC layer (which is responsible for scheduling transmissions) and the PHY layer (which manages actual transmission and reception of data over the media). [10] [11]

In some communications channels (for example, in power lines), noise and interference may be non-stationary and might vary synchronously with the 50 or 60 Hz AC current cycle. In scenarios like this, the overall system performance can be improved if the MAC can get information from the PHY regarding when and how the noise and interference level is changing, so that the MAC can schedule transmission during the periods of time in which noise and interference levels are lower. [11]

An example of a communications system that allows this kind of Cross-layer optimization is the ITU-T G.hn standard, which provides high-speed local area networking over existing home wiring (power lines, phone lines and coaxial cables).

Issues

Some issues may arise with cross-layer design and optimization by creating unwanted effects as explained in. [12] [13] Cross-layer design solutions that allow optimized operation for mobile devices in the modern heterogeneous wireless environment are described in, [14] where in addition the major open technical challenges in the cross-layer design research area are pointed out.

See also

Related Research Articles

IEEE 802.15 is a working group of the Institute of Electrical and Electronics Engineers (IEEE) IEEE 802 standards committee which specifies Wireless Specialty Networks (WSN) standards. The working group was formerly known as Working Group for Wireless Personal Area Networks.

A MAC address is a unique identifier assigned to a network interface controller (NIC) for use as a network address in communications within a network segment. This use is common in most IEEE 802 networking technologies, including Ethernet, Wi-Fi, and Bluetooth. Within the Open Systems Interconnection (OSI) network model, MAC addresses are used in the medium access control protocol sublayer of the data link layer. As typically represented, MAC addresses are recognizable as six groups of two hexadecimal digits, separated by hyphens, colons, or without a separator.

<span class="mw-page-title-main">OSI model</span> Model of communication of seven abstraction layers

The Open Systems Interconnection (OSI) model is a reference model from the International Organization for Standardization (ISO) that "provides a common basis for the coordination of standards development for the purpose of systems interconnection." In the OSI reference model, the communications between systems are split into seven different abstraction layers: Physical, Data Link, Network, Transport, Session, Presentation, and Application.

<span class="mw-page-title-main">Time-division multiple access</span> Channel access method for networks using a shared communications medium

Time-division multiple access (TDMA) is a channel access method for shared-medium networks. It allows several users to share the same frequency channel by dividing the signal into different time slots. The users transmit in rapid succession, one after the other, each using its own time slot. This allows multiple stations to share the same transmission medium while using only a part of its channel capacity. Dynamic TDMA is a TDMA variant that dynamically reserves a variable number of time slots in each frame to variable bit-rate data streams, based on the traffic demand of each data stream.

In the seven-layer OSI model of computer networking, the physical layer or layer 1 is the first and lowest layer: the layer most closely associated with the physical connection between devices. The physical layer provides an electrical, mechanical, and procedural interface to the transmission medium. The shapes and properties of the electrical connectors, the frequencies to transmit on, the line code to use and similar low-level parameters, are specified by the physical layer.

In telecommunications and computer networks, a channel access method or multiple access method allows more than two terminals connected to the same transmission medium to transmit over it and to share its capacity. Examples of shared physical media are wireless networks, bus networks, ring networks and point-to-point links operating in half-duplex mode.

The data link layer, or layer 2, is the second layer of the seven-layer OSI model of computer networking. This layer is the protocol layer that transfers data between nodes on a network segment across the physical layer. The data link layer provides the functional and procedural means to transfer data between network entities and may also provide the means to detect and possibly correct errors that can occur in the physical layer.

<span class="mw-page-title-main">Medium access control</span> Service layer in IEEE 802 network standards

In IEEE 802 LAN/MAN standards, the medium access control (MAC), also called media access control, is the layer that controls the hardware responsible for interaction with the wired or wireless transmission medium. The MAC sublayer and the logical link control (LLC) sublayer together make up the data link layer. The LLC provides flow control and multiplexing for the logical link, while the MAC provides flow control and multiplexing for the transmission medium.

<span class="mw-page-title-main">Beam tilt</span> Aiming of an antenna radiation pattern below the horizontal plane

Beam tilt is used in radio to aim the main lobe of the vertical plane radiation pattern of an antenna below the horizontal plane.

Network congestion in data networking and queueing theory is the reduced quality of service that occurs when a network node or link is carrying more data than it can handle. Typical effects include queueing delay, packet loss or the blocking of new connections. A consequence of congestion is that an incremental increase in offered load leads either only to a small increase or even a decrease in network throughput.

A cognitive radio (CR) is a radio that can be programmed and configured dynamically to use the best channels in its vicinity to avoid user interference and congestion. Such a radio automatically detects available channels, then accordingly changes its transmission or reception parameters to allow more concurrent wireless communications in a given band at one location. This process is a form of dynamic spectrum management.

<span class="mw-page-title-main">Computer network</span> Network that allows computers to share resources and communicate with each other

A computer network is a set of computers sharing resources located on or provided by network nodes. Computers use common communication protocols over digital interconnections to communicate with each other. These interconnections are made up of telecommunication network technologies based on physically wired, optical, and wireless radio-frequency methods that may be arranged in a variety of network topologies.

Dynamic spectrum management (DSM), also referred to as dynamic spectrum access (DSA), is a set of techniques based on theoretical concepts in network information theory and game theory that is being researched and developed to improve the performance of a communication network as a whole. The concept of DSM also draws principles from the fields of cross-layer optimization, artificial intelligence, machine learning etc. It has been recently made possible by the availability of software radio due to development of fast enough processors both at servers and at terminals. These are techniques for cooperative optimization. This can also be compared or related to optimization of one link in the network on the account of losing performance on many links negatively affected by this single optimization.

Radio resource management (RRM) is the system level management of co-channel interference, radio resources, and other radio transmission characteristics in wireless communication systems, for example cellular networks, wireless local area networks, wireless sensor systems, and radio broadcasting networks. RRM involves strategies and algorithms for controlling parameters such as transmit power, user allocation, beamforming, data rates, handover criteria, modulation scheme, error coding scheme, etc. The objective is to utilize the limited radio-frequency spectrum resources and radio network infrastructure as efficiently as possible.

Multi-user MIMO (MU-MIMO) is a set of multiple-input and multiple-output (MIMO) technologies for multipath wireless communication, in which multiple users or terminals, each radioing over one or more antennas, communicate with one another. In contrast, single-user MIMO (SU-MIMO) involves a single multi-antenna-equipped user or terminal communicating with precisely one other similarly equipped node. Analogous to how OFDMA adds multiple-access capability to OFDM in the cellular-communications realm, MU-MIMO adds multiple-user capability to MIMO in the wireless realm.

<span class="mw-page-title-main">MIMO</span> Use of multiple antennas in radio

In radio, multiple-input and multiple-output (MIMO) is a method for multiplying the capacity of a radio link using multiple transmission and receiving antennas to exploit multipath propagation. MIMO has become an essential element of wireless communication standards including IEEE 802.11n, IEEE 802.11ac, HSPA+ (3G), WiMAX, and Long Term Evolution (LTE). More recently, MIMO has been applied to power-line communication for three-wire installations as part of the ITU G.hn standard and of the HomePlug AV2 specification.

Game theory has been used as a tool for modeling and studying interactions between cognitive radios envisioned to operate in future communications systems. Such terminals will have the capability to adapt to the context they operate in, through possibly power and rate control as well as channel selection. Software agents embedded in these terminals will potentially be selfish, meaning they will only try to maximize the throughput/connectivity of the terminal they function for, as opposed to maximizing the welfare of the system they operate in. Thus, the potential interactions among them can be modeled through non-cooperative games. The researchers in this field often strive to determine the stable operating points of systems composed of such selfish terminals, and try to come up with a minimum set of rules (etiquette) so as to make sure that the optimality loss compared to a cooperative – centrally controlled setting – is kept at a minimum.

A communication protocol is a system of rules that allows two or more entities of a communications system to transmit information via any variation of a physical quantity. The protocol defines the rules, syntax, semantics, and synchronization of communication and possible error recovery methods. Protocols may be implemented by hardware, software, or a combination of both.

Guowang Miao is a system engineer and researcher focusing on next-generation mobile Internet and wireless systems. He researches primarily the design, signal processing, and optimization of cloud platforms and networking systems. He is the author of Fundamentals of Mobile Data Networks and Energy and Spectrum Efficient Wireless Network Design.

Ness B. Shroff is an American engineer, educator and researcher known for contributions to wireless networking, network control, and network analysis. He is professor in ECE and CSE departments at Ohio State University, where he holds the Ohio Eminent Scholar Chaired Professorship of Networking and Communications.

References

  1. ↑ http://www.ece.purdue.edu/~shroff/Shroff/journal/LSS06.pdf%5B%5D
  2. ↑ "Archived copy" (PDF). Archived from the original (PDF) on 2008-07-04. Retrieved 2008-06-25.{{cite web}}: CS1 maint: archived copy as title (link)
  3. ↑ "IETE Technical Review : Paid Content". Archived from the original on 15 April 2013.
  4. ↑ "Archived copy" (PDF). Archived from the original (PDF) on 2008-05-16. Retrieved 2008-06-25.{{cite web}}: CS1 maint: archived copy as title (link)
  5. 1 2 Cognitive Radio Communications and Networks : Principles and Practice . Burlington, MA: Academic Press. 2010. pp.  201–234. ISBN   9780080879321.
  6. ↑ Karmokar, Ashok (21 November 2012). "Energy-Efficient Green Radio Communications for Delay Tolerant Applications". Handbook of Green Information and Communication Systems: 183–208. doi:10.1016/B978-0-12-415844-3.00007-3. ISBN   9780124158443.
  7. ↑ Wymeersch, Henk (2016). "Multiple access control in wireless networks". Academic Press Library in Mobile and Wireless Communications. Academic Press. pp. 435–465. doi:10.1016/B978-0-12-398281-0.00012-0. ISBN   978-0-12-398281-0.
  8. ↑ "Cross-layer integrated collision free path routing - US Patent 7339897". Archived from the original on 2011-06-12. Retrieved 2008-06-25.
  9. ↑ http://www.nyman-workshop.org/2003/papers/Cross-Layer%20Optimization%20for%20Sensor%20Networks.pdf Archived 2008-08-28 at the Wayback Machine [ bare URL PDF ]
  10. ↑ S. Shabdanov, P. Mitran, C. Rosenberg, "Cross-Layer Optimization Using Advanced Physical Layer Techniques in Wireless Mesh Networks", in IEEE Transactions on Wireless Communications
  11. 1 2 Guowang Miao; Guocong Song (2014). Energy and spectrum efficient wireless network design. Cambridge University Press. ISBN   978-1107039889.
  12. ↑ V. Kawadia, P.R. Kumar, "A cautionary perspective on cross-layer design", in: IEEE Wireless Communications, Volume 12, Issue 1, Feb. 2005.[ dead link ]
  13. ↑ P. Papadimitratos, A. Mishra, and D. Rosenburgh, "A Cross-Layer Design Approach to Enhance 802.15.4", in: IEEE MILCON 2005, Volume 3, pp 1719-1726, June 2005
  14. ↑ F. Foukalas et al., "Cross-layer design proposals for wireless mobile networks: a survey and taxonomy "
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