Bandwidth Allocation Granularity Research Articles

QoT-aware adaptive modulation format-based resource provisioning for clustered LR-PON

• This study presents a QoT-aware adaptive modulation format based on resource provisioning (QAMF-RP) algorithm for software-defined long-reach passive optical networks architecture. • The LR-PON architecture incorporates orthogonal frequency division multiplexing-based time-wavelength division multiplex PON (OFDM-based-TWDM-PON), thus high bandwidth utilisation and small bandwidth allocation granularity with limited network resources is possible to deal with this rapid traffic growth. • What’s more, the proposed QAMF-RP algorithm addresses the challenges associated with the higher upstream channel idle time owing to long round trip time and data-reliable transmission for all types of services. • We believe that our study makes a significant contribution to the literature because our results show a promising performance of the proposed system that significantly reduce average latency, improve throughput and network QoS, ensure optimal resource provisioning, and satisfy various service requirements. The range of conventional passive optical networks (PONs) is 20 km, which are difficult to satisfy the requirements of accommodating increasing number of users and coverage areas. Thus, a software-defined long-reach PON (LR-PON) architecture which extends the access network to hundreds of kilometres is proposed in this paper. Using the proposed LR-PON architecture, which incorporates orthogonal frequency division multiplexing-based time-wavelength division multiplex PON (OFDM-based-TWDM-PON), high bandwidth utilisation and small bandwidth allocation granularity with limited network resources is possible to deal with this rapid traffic growth. Further, to address major challenges such as higher upstream channel idle time owing to long round trip time and data-reliable transmission for all types of services, while considering energy consumption, we also propose a quality-of-transmission (QoT)-aware adaptive modulation format-based resource provisioning algorithm that considers the PHY and MAC layers. The results of simulations conducted to verify the performance of the proposed architecture and algorithm demonstrate that they can reduce average latency, significantly improve throughput and network QoS, ensure optimal resource provisioning, and satisfy various service requirements.

Minimizing Blocking Probability in Elastic Optical Networks by Varying the Bandwidth Granularity Based on Optical Path Fragmentation

Elastic optical networks (EONs) based on orthogonal frequency-division multiplexing (OFDM) are considered a promising solution for the next optical network’s generation. These networks make it possible to choose an adequate portion of the available spectrum to satisfy the requested capacity. In this paper, we consider the impact of spectrum fragmentation along the optical single/multipath routing transmission on the efficiency of the EONs. This involves reducing the fragmentation effects by dynamically updating and controlling the minimum bandwidth allocation granularity (ɡ). We adopt linear and nonlinear dynamic mechanisms, which are denoted as LDAɡ and NLDAɡ, respectively, to choose proper bandwidth granularities that are proportional to the optical link/path bandwidth fragmentation status. In order to avoid either splitting the capacity request over many routing paths, which would increase the management complexity, or encouraging single path transmission, the proposed schemes aim to choose a proper bandwidth allocation granularity (ɡ) for a predefined set of suggested values. Simulation results show that varying the bandwidth granularity based on the optical path fragmentation status can offer an improved performance over fixed granularity with respect to the bandwidth blocking probability, the number of path splitting actions, the throughput, and the differential delay constraint issue in terms of: the network bandwidth utilization and multipath distribution.

Minimizing Blocking Probability in Elastic Optical Networks by Varying the Bandwidth Granularity Based on Optical Path Fragmentation

Elastic optical networks (EONs) based on orthogonal frequency-division multiplexing (OFDM) are considered a promising solution for the next optical network’s generation. It basically makes it possible to choose an adequate portion of the available spectrum to satisfy the requested capacity. In this paper, we consider the impact of spectrum fragmentation along the optical single/multipath routing transmission on the efficiency of the EONs. This involves reducing the fragmentation effects by dynamically updating and controlling the minimum bandwidth allocation granularity (g).We adopt linear and nonlinear dynamic mechanisms, which are denoted as LDAEi and NLDAEi, respectively, to choose proper band width granularities that are proportional to the optical link/path bandwidth fragmentation status. In order to avoid neither splitting the capacity request over many routing paths, which would increase the management complexity, nor encouraging single path transmission, the proposed schemes aim to choose a proper bandwidth allocation granularity (g) of a predefined set of suggested values. Simulation results show that varying the bandwidth granularity based on the optical path fragmentation status can offer improved performance over fixed granularity with respect to the bandwidth blocking probability, the number of path splitting, the throughput, and differential delay constraint issue in terms of: the network bandwidth utilization and multipath distribution.

Design and Evaluation of Elastic Optical Access Network Based on WDM-PON and OFDM Technology

The elastic optical network is a novel idea that is targeted at realizing flexible bandwidth allocation according to diverse traffic needs and requirements. Meanwhile, with the increasing demand of data rates in optical access networks, it is urgent to upgrade the current passive optical networks (PONs) through more elastic approaches. In this paper, we propose a kind of elastic optical access network based on wavelength-division multiplexing PON (WDM-PON) and orthogonal frequency-division multiplexing (OFDM) technology, in which finer bandwidth allocation granularity and a flexible wavelength switch are realized. We simulate the transmission performance of the system in both uplinks and downlinks.We also evaluate the elasticity of the system and propose an improved dynamic bandwidth allocation algorithm that has been shown to be the most effective in reducing the blocking rate and bandwidth fragmentation.

GoS Evaluation for OFDMA Cellular Networks

Analytical methods on grade of service (GoS, quantified by the blocking probability which is denoted as $$P_b$$Pb) evaluation in orthogonal frequency division multiple access cellular networks for real-time traffic are important for cell-dimensioning. Existing works use simplified spectral efficiency (SE) models that lead to conservative outcomes. For computing cell-wide and cell-average $$P_b$$Pb the exact but mathematically intractable Kaufman Roberts algorithm (KRA) is indispensable. The Erlang approximation (EA) tractably computes only cell-average $$P_b$$Pb but ignores bandwidth allocation granularity leading to an error of around 25 % in typical scenarios. In this work, by using an accurate SE model we show a significant reduction in projected base station (BS) density requirement for maintaining satisfactory cell-average $$P_b$$Pb. We show that cell-average $$P_b$$Pb does not completely depict the GoS situation within a cell since there is significant variation of $$P_b$$Pb inside it. Further, we enhance the EA in two ways. Firstly, we improve its accuracy to within 2 % of KRA by accounting for bandwidth allocation granularity. Secondly, we extend it to compute cell-wide $$P_b$$Pb like the KRA. The resulting method helps to explain properties such as the linearly increasing trend of region-wise $$P_b$$Pb versus region-index in case of low bit-rate streaming calls. We also use the aforementioned linearly increasing trend to arrive at another alternative to KRA. The development of these two alternatives to KRA highlights certain interesting properties of region-wise and cell-average $$P_b$$Pb as well as the EA. The error in estimated BS density requirement with these alternatives in case of 12.2 kbps voice in the interference limited situation is negligibly small. We employ discrete event simulations to validate our models.

Dynamic Multi-Path Service Provisioning under Differential Delay Constraint in Elastic Optical Networks

Optical orthogonal frequency-division multiplexing (O-OFDM) technology has the elastic feature of allocating spectrum resources based on subcarrier slots with bandwidths at a few GHz or even narrower. This feature enables us to utilize link capacity more efficiently by splitting a connection's traffic over multiple routing paths. In this paper, we propose a novel dynamic multi-path provisioning algorithm for O-OFDM based elastic optical networks. The algorithm tries to set up dynamic connections with single-path routing in a best-effort manner. When a connection cannot be served with a single routing path, the algorithm uses an auxiliary-graph based approach to calculate a multi-path provisioning scheme based on two parameters, i.e., the differential delay upper-bound and the bandwidth allocation granularity. Simulation results indicate that compared with several existing single-path provisioning algorithms, the proposed algorithm provides lower bandwidth blocking probability and achieves 10-18% improvement on average network throughput.

Migration Strategies Toward All Optical Metropolitan Access Rings

Nowadays, network operators are steadily deploying optical circuit switching (OCS) equipment in their metropolitan networks in order to cope with traffic increase and, most importantly, in order to reduce capital expenditures and operational expenditures of existing active technologies. On the other hand, optical burst switching (OBS) technology is expected to become mature in the medium term, and it may be used as an alternative to current OCS networks due to its potential advantages in terms of bandwidth allocation granularity. While OBS is being extensively studied in the literature, little attention has been paid in conducting a comparative analysis of OBS versus OCS, especially concerning cost analysis. In this paper, we provide a comparative analysis of OBS versus OCS as an evolutionary technology for all-optical rings in the metropolitan-access network. This paper is specifically targeted toward optimizing the number of optoelectronic receivers and wavelengths with real traffic matrices from the metropolitan rings in Madrid, Spain. Such matrices also include traffic projections of foreseeable broadband services, which are based on a market analysis from the largest operator in Spain. Our findings show that OCS might be more efficient than OBS in the metro-access segment, which is characterized by a highly centralized traffic pattern. However, the more distributed the traffic is, the more efficient the OBS is as well. Consequently, OBS might be better suited to metro-core networks, which show a more distributed and dynamic traffic pattern.

New queueing strategies employing service interval-based priority for real-time communications in atm networks

In this paper, we propose queueing strategies employing the service interval-based priority (sip) which can provide delay-bounded, and loss-free services, while maximizing bandwidth utilization in the atm network. We also describe a variation of the sip, the residual service interval-based priority (rsip) which can achieve almost full utilization by assigning priorities dynamically on the basis of the residual service interval. We store the realtime cells belonging to different connections in logically separated queues, and for each queue, we set a parameter called service interval, during which only one cell is allowed to be transmitted. The sip server takes and transmits the head-of-line (hol) cell of the queue which has the smallest service interval, while the rsip server selects the queue with the smallest residual service interval. When there is no eligible real-time cell, it transmits non-real-time cell, thus enabling a maximized bandwidth utilization. Employing the above queueing strategies, we analyze the delay characteristics deterministically with the leaky bucket bounded input traffic and then dimension the optimal service interval. In dimensioning the service interval and buffer space of each real-time service queue, we consider burstiness of traffic in conjunction with delay constraints, so that bandwidth utilization can get maximized. In addition, we consider the issues of protection from malicious users, average bandwidth utilization, and coupling between the delay bound and the bandwidth allocation granularity.