Unicast Channels Research Articles

MMNNN: A tree-based Multicast Mechanism for NoC-based deep Neural Network accelerators

Network-on-Chip (NoC) devices have been widely used in multiprocessor systems. In recent years, NoC-based Deep Neural Network (DNN) accelerators have been proposed to connect neural computing devices using NoCs. Such designs dramatically reduce off-chip memory accesses of these platforms. However, the large number of one-to-many packet transfers significantly degrade performance with traditional unicast channels. We propose a multicast mechanism for a NoC-based DNN accelerator called Multicast Mechanism for NoC-based Neural Network accelerator (MMNNN). To do so, we propose a tree-based multicast routing algorithm with excellent scalability and the ability to minimize the number of packets in the network. We also propose a router architecture for single-flit packets. Our proposed router transfers flits to multiple destinations in a single process and has no head-of-line blocking issue, offering higher throughput and lower latency than traditional wormhole router architectures. Simulation results show that our proposed multicast mechanism offers excellent performance in classification latency, average packet latency, and energy consumption.

An Efficient Content Distribution Network Architecture Using Heterogeneous Channels

With the popularization and development of the IoT(Internet of Things), more and more data needs to be transmitted over the Internet, which leads to the deterioration of network quality. The CDN (Content Distribution Network) technology is an important theoretical model to ensure network QoS (Quality of Service). To improve the QoS, we extend current CDN system to the hierarchical CDN system, that traditional CDN system is just a special case of hierarchical CDN system. In the traditional CDN system and the hierarchical CDN system, by analyzing the bandwidth between subsystems, we found the inter-system bandwidth is the bottleneck that impedes CDN system expansion. To address this problem, a new kind of distributed system architecture is proposed in this paper. This new architecture uses broadcast channels to distribute broadcast type data and still using bidirection uni-cast channels for other type of data, so we call the new architecture as CHCDN (Channel Heterogeneous CDN) in this paper. The new architecture is analyzed and compared with the traditional CDN system architecture and hierarchical CDN system architecture. Moreover, the experimental simulation result has shown that the CHCDN system features better in real-time cache updating and features with higher data transmission efficiency than the hierarchical CDN system, which indicating that the new architecture has great potential for being widely used in distributed computing.

An SDN-Based Video Multicast Orchestration Scheme for 5G Ultra-Dense Networks

Predictions indicate that mobile video streams will dominate mobile traffic in the near future. Heterogeneous UDN is a promising technique for 5G mobile networks. This technique offers high access speeds for video watchers through the dense deployment of small cells. However, the backhaul of a UDN will become a bottleneck with the rapid increase in mobile video traffic. Additionally, the considerable video traffic generated from and to UDNs induces significant stress on the core network of a 5G network. Therefore, it is necessary to optimize the distribution of video content for 5G UDNs. Multicasting is considered to be a good communication method for distributing video content. This article examines a video multicast orchestration scheme based on SDN, named HCM, for 5G UDNs. To adapt well to a heterogeneous UDN environment in 5G networks and effectively save spectrum resources, HCM implements wireless multicast functionality based on a common unicast channel. HCM performs concurrent multicasting to clearly reduce the bandwidth consumption of a 5G network, particularly the backhaul, and further controls video traffic passed through the backhaul using a traffic-aware method. During the packet loss recovery of HCM, SDN-based elastic area multicast is used to more effectively retransmit recovered packets. The experimental results indicate that our proposed scheme can distribute video content with high effectiveness.

Performance analysis of long reach colorless wavelength division multiplexed-orthogonal frequency division multiplexing-passive optical network with broadcast capability

A colorless wavelength division multiplexed-orthogonal frequency division multiplexing-passive optical network (WDM-OFDM-PON) is presented, which is capable of supporting symmetric 10 Gbps downlink direct detection (DD) OFDM unicast signal, broadcast signal, and uplink on–off keying (OOK) signal up to 60 km that includes both single mode and dispersion compensation fiber. At each optical network unit (ONU), DD has been used to receive downlink unicast and broadcast OFDM data. A delay interferometer (DI) has been used at a central office to achieve 10 Gbps uplink signal transmission over 60 km distance utilizing a reflective semiconductor optical amplifier (bandwidth=1.5 GHz) at the ONU because DI works as a vestigial sideband filter and an optical equalizer. Broadcast channel does not affect the system performance because it generates a limited interference of the order of 0.1 to 0.28 dB to downlink and uplink channels, and this interference is distributed to every ONU. For bit error rate of 10−9, the receiver sensitivity of −24, −23.1, and −20.14 dBm is achieved by simulating downlink OFDM unicast channels, OFDM broadcast channel, and uplink OOK unicast channels, respectively, for a symmetric data rate of 10 Gbps over 60 km.

Popularity–Based Adaptive Content Delivery Scheme with In-Network Caching

To solve the increasing popularity of video streaming services over the Internet, recent research activities have addressed the locality of content delivery from a network edge by introducing a storage module into a router. To employ in-network caching and persistent request routing, this paper introduces a hybrid content delivery network (CDN) system combining novel content routers in an underlay together with a traditional CDN server in an overlay. This system first selects the most suitable delivery scheme (that is, multicast or broadcast) for the content in question and then allocates an appropriate number of channels based on a consideration of the content's popularity. The proposed scheme aims to minimize traffic volume and achieve optimal delivery cost, since the most popular content is delivered through broadcast channels and the least popular through multicast channels. The performance of the adaptive scheme is clearly evaluated and compared against both the multicast and broadcast schemes in terms of the optimal in-network caching size and number of unicast channels in a content router to observe the significant impact of our proposed scheme.

Unicasting on the Secrecy Graph

We consider the secrecy capacity of unicast channels of ad hoc networks exposed to randomly located eavesdroppers, as modeled by S-Graphs. Expressions that quantify the impact of fading and of the density of legitimate nodes relative to that of eavesdroppers are obtained, in terms of the probability that secrecy capacities of unicast channels are nonzero. The results indicate that depending on the relative density of eavesdroppers and the fading intensity, the secrecy capacity of unicast channels subject to fading may be higher than under additive white Gaussian noise (AWGN).

Enhanced colorless and broadcast capable symmetrical 10-Gbps bidirectional transmission in WDM-PON using RSOA and EAM

Here we proposed a novel architecture of wavelength division multiplexed-passive optical network (WDM-PON) in which the downlink unicast data, broadcast data and uplink unicast data transmission is possible with the symmetric data rate of 10Gbps. At remote node (RN) cyclic wavelength routing property of array waveguide grating (AWG) and power splitting capacity of power splitter is used in the architecture so that broadcast channel can be overlaid on downlink unicast channels. At ONU carriers sent from central office (CO) is reused for upstream data transmission with the help of integration of a reflective semiconductor amplifier (RSOA) and an electro-absorption modulator (EAM) so there is no need of extra laser sources at ONUs which makes them colorless. EAM can be operated at very high speed; a modulation bandwidth of tens of GHz can be achieved. Broadcast channel causes a limited interference with downlink and uplink unicast channels so it does not affect the system performance. Since each channel has different wavelength so NRZ data is used which eliminates expensive DPSK receivers and detection becomes very easy. Simulation is performed with all channels having data rate of 10Gbps having acceptable performance.

Improved multicast key management of Chinese wireless local area network security standard

Multicasting is an important business in the field of the wireless local area network (WLAN), because the access point (AP) usually has to send the same message to each station (STA) of a specific group, and broadcasting the message to this group is one of the most efficient ways of communication. Chinese WLAN security standard, called WLAN Authentication and Privacy Infrastructure (WAPI), has taken secure multicasting into account, and proposed a Multicast Key Management Protocol (MKMP), in which the multicast session key (MSK) is distributed to each STA over the secure unicast channel built between STA and AP one by one. It is clear that the MSK distribution is very inefficient in performance, especially when the number of STAs is very large. In this study, a new MSK distribution protocol is proposed, and it can be used to substitute the original protocol in WAPI. Analyses show that the proposed protocol can achieve needed security requirements, and is more efficient than the original one in WAPI. Now, WAPI has been in the process of ISO/IEC standard building, and thus the authors think that their proposal can ameliorate WAPI largely and promote its ISO/IEC standard building.

A Broadcast/Multicast-Capable Carrier-Reuse WDM-PON

A novel broadcast/multicast-capable carrier-reuse WDM-PON architecture is proposed. Utilizing the splitting capability of a power splitter and the cyclic property of an arrayed waveguide grating (AWG) at the remote node, the broadcast channel and a dedicated downlink unicast channel can be overlaid and subsequently transmitted to each optical network unit (ONU) simultaneously. Since each ONU can receive a common broadcast channel with electronically coded information, the multicast function can be implemented in a higher layer, similar to the current multicast-capable E-PON or G-PON using IP multicast addresses through a single wavelength channel. Thus, there is no need for reconfiguration of physical connections for multicast services. The proposed approach is different from the approach of overlaying DPSK multicast data onto NRZ unicast data using the same wavelength. As such, this approach does not require an expensive DPSK receiver at each ONU, and high receiver sensitivity can be achieved since there is no need to restrict the extinction ratio (ER) of the NRZ unicast data to a small value. Simulation studies show that this WDM-PON provides acceptable performance with one 10 Gb/s broadcast channel and thirty-two 10 Gb/s downlink unicast channels, and thirty-two 2.5 Gb/s uplink unicast channels. Another advantage of this WDM-PON is that the broadcast channel only causes a small interference with the downlink/uplink unicast channels, and it is shared by all the ONUs. The effect of the optical carrier to subcarrier ratio on the bit error rate performance can be mitigated by increasing the extinction ratio of the delay interferometer used at the remote node.

Efficient Use of Multicast and Unicast Channels for Multicast Service Transmission

To overcome the problem that the transmission rate of a multicast channel is limited by the user with the worst channel quality, which causes the total system throughput to be low, the use of both multicast and unicast channels for multicast service is considered in this letter. Unicast channels, in addition to a multicast channel, are allocated to users with signal-to-noise ratios (SNRs) lower than a predefined threshold in order to enable the increase of the transmission rate of the multicast channel. The used unicast channels consume additional radio resource. It is examined whether use of such unicast channels can raise the spectral efficiency defined as the total system throughput normalized by the total consumed bandwidth. The optimal value of the threshold SNR is derived by maximizing the spectral efficiency. When a unicast channel is additionally allocated for multicast service, two decoding schemes are considered: one is to use only the signal of a unicast channel, and the other is to use and combine both the signals of multicast and unicast channels. Numerical examples are presented to show the performance gains obtained by using unicast channels in addition to a multicast channel.

Coherent detection passive optical access network enabling converged delivery of broadcast and dedicated broadband services

We propose a passive optical network architecture based on coherent detection for converged delivery of broadcast services from a dedicated remote broadcast server and user-specific services from a local central office. We experimentally demonstrate this architecture with mixed traffic types, wavelength division multiplexed, unicast channels composed of four radio-over-fiber channels operating at 5 GHz carrier frequency with 250 Mbaud phase shift keying modulation and four 10 Gb/s baseband amplitude shift keying channels; while the broadcast channels were four 10 Gbaud DQPSK channels. The broadcast channels were transmitted over 78 km of single mode fiber to a central office where they were multiplexed with the unicast channels for further fiber transmission over 34-km to reach the access network. Successful detection of all channels is demonstrated.

Request based data delivery in video-on-demand services

In unified video-on-demand (UVoD) architecture, the logical channels are classified as multicast and unicast channels. The multicast channels provide services periodically and are independent of the user requests, whereas the unicast channels are used to provide services to the individual users. In that architecture, the optimal number of unicast channels has been reported to be independent of the request arrival rate. This result seems to be less accurate as the number of logical channels is affected by the request arrival rate. In this paper, we propose a more accurate study in which the number of unicast channels is shown to be explicitly dependent on the request arrival rate. In addition, for providing immediate services to the users, the number of unicast channels is much less than that of the UVoD architecture. The other important point of this study is that it can provide services for both less popular and more popular videos. However, for more popular videos all channels should be multicast channels

Demonstration of an optical-label switching router with multicast and contention resolution at mixed data rates

This letter experimentally demonstrates a scalable optical-label switching router architecture that supports a limited multicast function. A semiconductor-optical-amplifier-based Mach-Zehnder interferometer wavelength converter performs multiwavelength conversion for multicast at 10 Gb/s by cross-phase modulation. With a 2.5-Gb/s unicast channel, the experiment also demonstrates contention resolution in the wavelength domain at mixed data rates.

P2P transfer of partial stream in multimedia multicast

In this paper, we propose a new multicast scheme that is based on the client-initiated-with-prefetching (CIWP) and peer-to-peer (P2P) transfer of a partial multimedia stream. In the CIWP scheme, when a new client joins an ongoing multicast channel, the server has to create an extra unicast channel to retransmit the partial stream that has already been transmitted. However, the unicast channel consumes some of the I/O bandwidth of the server, as well as some of the network resources between the server and the client's Internet Service Provider (ISP). To solve this problem, we propose the use of the P2P transfer algorithm to deliver the partial stream from a client that has already joined the ongoing multicast session to the newcomer. This P2P transfer between clients is limited to clients belonging to the same ISP. To further improve the performance, a threshold is used to control the P2P transfer. We performed analytical studies to show that the proposed multicast scheme can reduce the consumption of the network resources of the server, by utilizing the client's disk space. We also performed various simulation studies to demonstrate the performance improvement in terms of the use of the server's bandwidth and the waiting time for the clients’ requests.

Multimedia Information Delivery Over Wireless Channels

Wireless communication channels are generally characterized by availability of low bandwidth. Hence, exchange of multimedia information is normally done over a single or unicast channel. Multimedia information presentation can have certain constraints, such as precedence of one page of information with respect to another or the time of availability of information. Multimedia information delivery needs to be scheduled based on these constraints. In this paper, we model this scheduling problem using linear programming approach. We suggest the use of approximation algorithms proposed for this purpose (L.A. Hall, A.S. Schulz, D.R. Shmoys, and J. Wein, Mathematics of Operations Research, Vol. 22, pp. 513–544, 1997). We have also presented the use of on-line approximation algorithms for scheduling multimedia information delivery when their availability varies with time. We have presented our implementation experience also.

Design of cascade ring multicast switch

A new high performance multicast switch is presented which consists of two independent subnetworks in tandem: a unicast subnetwork (USN) and a multicast subnetwork (MSN). Some of the unicast output channels are connected to the multicast ring subnetwork. This switch is approximately analysed with an equivalent queueing system to estimate the service capability seen by each input.