A secondary telecommunications channel that resides within the main channel (a carrier within a carrier). A type of multiplexing, the subcarrier is a modulated carrier signal at a lower frequency that is combined with the main carrier signal running at a higher frequency.
Many Uses
Color TV signals were added in a subcarrier to black and white signals in order to maintain backward compatibility with monochrome TV sets. Stereo was added to FM radio in a subcarrier for compatibility. Subcarriers are also often used to provide the audio channel in a video broadcast. See carrier.
Many Uses
Color TV signals were added in a subcarrier to black and white signals in order to maintain backward compatibility with monochrome TV sets. Stereo was added to FM radio in a subcarrier for compatibility. Subcarriers are also often used to provide the audio channel in a video broadcast. See carrier.
 | Reproduced with permission from Computer Desktop Encyclopedia. Copyright (c) 1981-2009 The Computer Language Company Inc. All rights reserved. |
Additional Resources
- Radio-Over-Fiber Transmission of 1.25-Gigabit Ethernet Signal on 60-GHz Band Subcarrier With Performance Improvement and Wavelength Reuse
- With Radio-over-Fiber RoF enabled remote antenna, Gigabit Ethernet service operating at 60-GHz frequencies can be accessed cordlessly. Due to limited linear operation region of 60-GHz optoelectronic modulators commercially available so far, optical weak modulation is required leading to limited link performance. This paper demonstrates in RoF transmission of 1.25-Gigabit Ethernet...
- White papers 2007-06-01
- Optimal Scheduling for OFDMA Systems
- This paper considers a scheduling and resource allocation problem for the downlink of an OFDMA-based wireless network, where the channel estimation error is modeled by a self-noise term in the decoding process. During each time-slot this involves selecting a subset of users for transmission, determining the assignment of available subcarriers...
- White papers 2006-11-24
- Adaptive OFDM Techniques With One-Bit-Per-Subcarrier Channel-State Feedback
- In the Orthogonal Frequency-Division Multiplexing OFDM scheme, some subcarriers may be subject to a deep fading. Adaptive techniques can be applied to mitigate this effect if the Channel-State Information CSI is available at the transmitter. This paper studies the performance of an OFDM-based communication system whose transmitter has only one...
- White papers 2006-11-01
- Linear Precoding for Multiuser MIMO-OFDM Systems
- This paper develops linear precoding schemes for the downlink in multiuser Multiple-Input Multiple-Output MIMO Orthogonal Frequency Division Multiplexing OFDM systems with multiple data streams per user. The authors extend an existing multiuser MIMO algorithm, that jointly optimizes the power allocation and the transmit and receive filters, to MIMOOFDM systems. One...
- White papers 2006-09-28
- Delay Analysis and Comparison of OFDM-TDMA and OFDMA Under IEEE 802.16 QoS Framework
- The delay analysis and comparison of OFDM-TDMA and OFDMA using a flow control scheme under the QoS framework of IEEE 802.16 are conducted in the work discussed in this paper. The paper investigates the maximum packet delay performance by deriving delay bounds for several multiaccess modes with different subcarrier/time-slot assignment...
- White papers 2006-07-22
- On the Use of Adaptive Loading Algorithms in MIMO-OFDM Systems
- In this paper, Optimum adaptive loading algorithms are applied to Multiple-Input Multiple-Output Orthogonal Frequency Division Multiplexing MIMOOFDM system. Chaw's and Compello's algorithms have been implemented to obtain a bit and power allocation for each subcarrier assuming instantaneous channel knowledge. Channel matrix Singular Value Decomposition SVD method has been employed in...
- White papers 2006-04-19
- Downlink Scheduling and Resource Allocation for OFDM Systems
- This paper considers scheduling and resource allocation for the downlink of a OFDM-based wireless network. During each time-slot the scheduling and resource allocation problem involves selecting a subset of users for transmission, determining the assignment of available subcarriers to selected users, and for each subcarrier determining the transmission power and...
- White papers 2006-02-27
- Performance Analysis of a Reuse Partitioning Technique for OFDM Based Evolved UTRA
- The current 3GPP working assumption on the Evolved Universal Terrestrial Radio Access (E-UTRA) physical layer is that it will be based on Single Carrier Frequency Division Multiple Access (SC-FDMA) for the uplink and Orthogonal Frequency Division Multiple Access OFDMA for the downlink. According to the concept specification, inter-cell interference mitigation...
- White papers 2006-02-01
- Resource Allocation in OFDMA Wireless Networks With Time-Varying Arrivals
- This paper considers the issue of optimal subcarrier allocation in OFDMA wireless networks when the arrivals and channels are stochastic and time-varying. The objective is to minimize the long-term average packet delay over multiple time epochs. This paper shows by example that water-filling-based subcarrier allocation policy which maximizes throughput at...
- White papers 2005-11-14
- Joint Allocation of Subcarriers and Transmit Powers in a Multiuser OFDM Cellular Network
- This paper considers the problem of joint bandwidth subcarriers and power allocation for the downlink of a multi-user multi-cell OFDM cellular network. This resource allocation problem is formulated as a power minimization problem, subject to meeting the target rates of all users in the network. The authors develop a distributed...
- White papers 2005-09-23
- Cross-Layer Optimization for OFDM Wireless Networks - Part II: Algorithm Development
- The authors have established a theoretical framework for cross-layer optimization in Orthogonal Frequency Division Multiplexing OFDM wireless networks. This paper focuses on effective and practical algorithms for efficient and fair resource allocation in OFDM wireless networks. The authors have taken various conditions into account and developed a variety of efficient...
- White papers 2005-03-01
- Rate Stable Resource Allocation in OFDM Systems: From Water-Filling to Queue-Balancing
- This paper considers the issue of optimal subcarrier allocation in OFDMA. The authors show, via a counter example, that water-filling based subcarrier allocation policies, contrary to conventional wisdom, fail to provide rate-stability for an otherwise stabilizable OFDMA system. Water-filling is too myopic when considering longtime average performance, e.g. delay, queue...
- White papers 2004-12-05
- A Fresh Look at Optimal Subcarrier Allocation in OFDMA Systems
- This paper considers the issue of optimal subcarrier allocation in OFDMA. This paper shows, via a counter example, that water-filling based subcarrier allocation policies, contrary to conventional wisdom, fail to provide rate-stability for an otherwise stabilizable OFDMA system. Water-filling is too myopic when considering long-time average performance, e.g. delay, queue...
- White papers 2004-09-09
- Capacity Analysis on Downlink MIMO OFDMA Systems
- Motivated by the increasing popularity of OFDMA and MIMO, this paper studies the capacity of MIMO enabled OFDMA system under a generic multiuser multicarrier framework. This paper shows that in terms of total system capacity, OFDMA is the optimal downlink scheme for independent decoding receivers. To achieve the capacity bound...
- White papers 2004-08-24
- Scalable OFDMA Physical Layer in IEEE 802.16 WirelessMAN
- The concept of scalability was introduced to the IEEE 802.16 WirelessMAN Orthogonal Frequency Division Multiplexing Access OFDMA mode by the 802.16 Task Group e TGe. A scalable physical layer enables standard-based solutions to deliver optimum performance in channel bandwidths ranging from 1.25 MHz to 20 MHz with fixed subcarrier spacing...
- White papers 2004-08-20
- Microsoft sets time for cyberwatches
- Microsoft sets time for cyberwatchesROFLAOYo...Boss man,..Um ....Like Sorry I'm late.....Um .My watch crashed...ROFLAOLet me guess..."Microsoft's Smart Personal Objects Technology SPOT and its subscription-based MSN Direct service will power the wristwatches, along with other devices to be released in the future."If you don't pay your monthly fee, your watch will stop...
- Discussion threads 2003-12-16
- M-QAM OFDM and PCC-OFDM Performance in the Presence of Phase Noise
- This paper addresses the issue of OFDM and PCC-OFDM systems impaired by phase noise PN. PCC-OFDM is a variation of OFDM in which data is mapped onto adjacent subcarrier pairs. As a result intercarrier interference ICI in adjacent subcarriers is cancelled. Phase noise in OFDM causes both ICI and common...
- White papers 2003-11-10
- A Proposal of Optical Wireless Communication With RF Subcarrier
- Optical wireless communication is safety for electric equipment, because it doesn't produce any electromagnetic waves. Therefore it is suitable for wireless communication on these places, and one needs to propose optical wireless access system for these places. And if one examines the characteristic of optical wireless communication, it is important...
- White papers 2003-09-09
- A Sub-Optimal Joint Subcarrier and Power Allocation Algorithm for Multiuser OFDM
- This paper investigates subcarrier and power allocation in multiuser OFDM. The aim is to maximize the overall rate while achieving proportional fairness amongst users under a total power constraint. Achieving the optimal solution is computationally demanding thereby necessitating the use of suboptimal techniques. Existing sub-optimal techniques either use fixed power...
- White papers
- Utility-Based Joint Physical-MAC Layer Optimization in OFDM
- In this paper, joint physical-MAC layer optimization in OFDM systems using adaptive modulation and subcarrier allocation is investigated based on utility theory. Since utility qualifies the level of users' satisfaction derived from the radio resources they occupy, it is ideal for a network optimization metric. The paper formulates cross-layer optimization...
- White papers
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