abhishek dixit - Academia.edu (original) (raw)

Papers by abhishek dixit

39th European Conference and Exhibition on Optical Communication (ECOC 2013), 2013

Time and wavelength division multiplexed passive optical networks (TWDM-PONs) have been widely ac... more Time and wavelength division multiplexed passive optical networks (TWDM-PONs) have been widely accepted as a next generation optical access (NGOA) solution. We propose a novel dynamic bandwidth allocation (DBA) algorithm for energy efficiency in TWDM-PONs.

2015 17th International Conference on Transparent Optical Networks (ICTON), 2015

Energy efficiency is of a vital significance in the design of next generation time and wavelength... more Energy efficiency is of a vital significance in the design of next generation time and wavelength division multiplexed passive optical networks (TWDM-PONs). In this paper, we first review strategies to save energy in TWDM-PONs using the state-of-the-art dynamic bandwidth allocation (DBA) algorithms. The DBA algorithms should not only minimize energy consumption but should impose a minimal penalty on delay performance. In this context, mainly two DBA design paradigms can be exploited: offline and online. After reviewing the performance of various design paradigms, we propose an optimal algorithm, which minimizes the energy consumption at both the OLT and the ONUs, by combining the energy efficiency due to sleep modes and the load dependent use of transceivers at the OLT. Due to this, the average energy consumption is reduced to 31%.

Journal of Lightwave Technology, 2015

This paper proposes an optical distribution network (ODN) architecture for open access networks. ... more This paper proposes an optical distribution network (ODN) architecture for open access networks. The proposed scheme ensures coexistence of multiple business partners (BPs) e.g., service, network equipment, and infrastructure providers at different levels of the distribution network, along with physicallayer security. Further, physical-layer isolation is provided to each subscriber, preventing network disruption by malicious subscribers. The proposed open access ODN supports BPs with different granularities (sizes) and discourages monopoly; thus, allowing multiple BPs to co-exist. It also supports incremental deployability (ID) which allows the BPs to cope with an expanding user base. Thus, small BPs can take up a market share with reasonable initial investment and grow with differential expenditures. ID further allows us to incrementally scale up the power consumption as a function of the network load, making the architecture green. The proposed ODN is based on a passive optical network (PON) architecture resulting in low operational expenditures (OpEx) and high availability. Besides a new ODN architecture, a novel architecture for the optical line terminal (OLT), based on hybrid time and wavelength-division multiplexing (TWDM), is proposed. The BPs can adopt typical TWDM, wavelength division multiplexing, or the TWDM-based OLT architecture (introduced in this paper) over the proposed ODN. Index Terms-Bandwidth flexibility, green access networks, open access networks, passive optical networks.

Photonic Network Communications, 2015

An ever-increasing bandwidth demand is the main driver to investigate next generation optical acc... more An ever-increasing bandwidth demand is the main driver to investigate next generation optical access (NGOA) networks. These networks, however, do not only have to comply with increasing data rates, they should also meet the societal green agenda. As the access part consumes a major fraction of the energy consumption in today's fiber-to-the-home (FTTH) based telecommunication networks, the energy efficiency of NGOA networks should be an important design parameter. In this paper, we present a detailed evaluation of the energy consumption in different NGOA technologies. Furthermore, we analyze the effects of (1) introducing low power modes (e.g., sleep and doze modes) in the various NGOA technologies and (2) using optimal split ratios adjusted to the traffic demands so that the energy consumption is optimized for the desired quality of service (QoS) level.

Next Generation Passive Optical Networks-2 (NG-PON2) are being considered to upgrade the current ... more Next Generation Passive Optical Networks-2 (NG-PON2) are being considered to upgrade the current PON technology to meet the ever increasing bandwidth requirements of the end users while optimizing the network operators' investment. Reliability performance of NG-PON2 is very important due to the extended reach and, consequently, large number of served customers per PON segment. On the other hand, the use of more complex and hence more failure prone components than in the current PON systems may degrade reliability performance of the network. Thus designing reliable NG-PON2 architectures is of a paramount importance. Moreover, for appropriately evaluating network reliability performance, new models are required. For example, the commonly used reliability parameter, i.e., connection availability, defined as the percentage of time for which a connection remains operable, doesn't reflect the network wide reliability performance. The network operators are often more concerned about a single failure affecting a large number of customers than many uncorrelated failures disconnecting fewer customers while leading to the same average failure time. With this view, we introduce a new parameter for reliability performance evaluation, referred to as the failure impact. In this paper, we propose several reliable architectures for two important NG-PON2 candidates: wavelength division multiplexed (WDM) PON and time and wavelength division multiplexed (TWDM) PON. Furthermore, we evaluate protection coverage, availability, failure impact and cost of the proposed schemes in order to identify the most efficient protection architecture.

Computer Networks, 2015

In this paper, the energy consumption of high speed access services up to 1 Gb/s per customer is ... more In this paper, the energy consumption of high speed access services up to 1 Gb/s per customer is estimated for different passive optical network (PON) technologies. While other studies on PON power consumption typically assume a fixed split ratio, we also consider a greenfield approach, where the split ratio can be optimized for each technology, taking full advantage of its capacity and reach. The split ratio optimization takes into account Quality of Service (QoS) in terms of bandwidth availability and packet loss for triple-play services (voice, television and Internet). This paper includes an in-depth discussion of our split ratio dimensioning approach and our power consumption model for an optical access network in a major city. The obtained results show that statistical gain provided by dynamic bandwidth allocation as well as power splitting ratio optimization in PONs are key factors for achieving energy efficiency. For access rates up to 900 Mb/s, XG-PON1 turns out to be the most energy efficient option. For higher access rates up to 1 Gb/s, the optimal technology depends on split ratio restrictions. If an existing optical distribution network (ODN) with split ratio 1:64 is used, XG-PON1 remains the most energy efficient technology. If higher split ratios up to 1:256 can be achieved, TWDM PON becomes the most energy efficient solution for access rates up to 1 Gb/s.

IEEE Network, 2014

There has been a large global effort to innovate and design optical access technologies that can ... more There has been a large global effort to innovate and design optical access technologies that can accommodate the requirements emerging from a colossal increase in data rates. Currently time and wavelength division multiplexed passive optical networks (TWDM-PONs) and WDM-PONs have been foreseen as the main candidates for next-generation access systems. Due to current business modeling trends and possible regulatory obligations, these networks should also support open access, which refers to the sharing of a network infrastructure among different network entities in a non-discriminatory way. By sharing the (bottleneck) infrastructure facility, open access reduces the entry barrier for a network entity. This opens doors for a multi-provider scenario, which leads to competition among network players and can significantly reduce the price of services. Opening up the network, however, entails new architectures. In this paper, we propose novel architectures to support open access at fiber and wavelength level for WDM-and TWDM-PON. These architectures, however, differ significantly in terms of their cost (capital and operational expenditures). We compare the proposed architectures with regard to their cost and analyze the impact of adoption levels (percentage of users subscribed) and customer churn rate (how often the customers change network) on the cost of the architectures.

2011 13th International Conference on Transparent Optical Networks, 2011

In this paper, we introduce a new dynamic bandwidth allocation (DBA) algorithm for long-reach pas... more In this paper, we introduce a new dynamic bandwidth allocation (DBA) algorithm for long-reach passive optical networks (LR-PON) based on the multi-threads (MT) polling algorithm. For the proposed new DBA algorithm, named as the Adaptive Multi-GAte polling with Void filling (AMGAV), the number of threads changes according to the traffic load of a PON in contrast to the static number of threads used in the MT polling algorithm. This makes the algorithm adaptive to load variations and it improves the delay performance for both higher and lower load scenarios. Moreover, the AMGAV algorithm requires no extra effort to enforce separation between threads which makes it simpler to implement than the MT polling algorithm. In the process, we also propose a novel bandwidth reporting scheme which does not have to keep track of the number of threads. Finally, through extensive simulations, we prove that for LR-PON, the AMGAV algorithm provides a better delay performance than the MT polling algorithm for a network load up to 90%, and a comparable performance at higher loads while improving the channel utilization.

2011 1st International Symposium on Access Spaces (ISAS), 2011

Introducing a WDM dimension on the top of a TDM PON system is a natural evolution to increase the... more Introducing a WDM dimension on the top of a TDM PON system is a natural evolution to increase the capacity of an optical access network, and this can also offer additional flexibility options. Several hybrid WDM/TDM PON architectures can be designed, each with a different degree of flexibility, going from fully static, over partially flexible to fully flexible architectures. The more flexible architectures, however, are either more expensive, experience a higher power loss or are less secure. A question that arises is if a fully flexible architecture is really needed, or if a partially flexible architecture already can serve several flexibility advantages, like energy efficiency, network migration and network extensibility. An important assessment parameter is the number of needed wavelengths at a certain network load. For a fully flexible architecture, it is clear that the number of needed wavelengths can be optimally minimized, but how big is the gain of a fully flexible architecture compared to a partially flexible one, and what is the minimum degree of flexibility required to have a significant advantage of the offered flexibility. In this paper we evaluate through simulation different architectural options for a hybrid WDM/TDM PON, in terms of flexibility. For this purpose, we use an underlined well-suited medium access control (MAC) protocol that exploits the offered flexibility in terms of dynamic wavelength allocation.

European Conference and Exhibition on Optical Communication, 2012

We propose a new dynamic bandwidth allocation algorithm for energy efficiency in next generation ... more We propose a new dynamic bandwidth allocation algorithm for energy efficiency in next generation optical access (NGOA) networks, and evaluate the power savings possible at the optical network unit (ONU) by applying sleep and doze modes. Sleep mode is found to be most effective for NGOA systems with burst mode traffic transmission and reception.

2012 IEEE International Conference on Communications (ICC), 2012

Hybrid WDM/TDM Passive Optical Network (PON) is a promising candidate for next-generation optical... more Hybrid WDM/TDM Passive Optical Network (PON) is a promising candidate for next-generation optical access (NGOA) solutions as it is able to offer a high splitting ratio and consequently achieves a relatively low cost and power consumption on a per-user basis compared with other NGOA architectures. On the other hand, the end users require a certain level of connection availability while the operators need to reduce the failure impact (i.e. to avoid a huge number of end users being affected by any single failure). Therefore, by evaluating the connection availability and failure impact robustness we identify the most efficient parts to provide resilience in a hybrid WDM/TDM PON from an operator and an end-user perspective. Then, we select the appropriate protection schemes to construct some novel reliable architectures and analyze their reliability performance in urban and rural scenarios. In this way, this paper provides a comprehensive insight into the most relevant protection mechanisms for hybrid WDM/TDM PONs.

2012 14th International Conference on Transparent Optical Networks (ICTON), 2012

In this paper, we propose the system concepts of a next-generation wavelength switched hybrid tim... more In this paper, we propose the system concepts of a next-generation wavelength switched hybrid time division multiple access and wavelength division multiplexing (TWDM) passive optical network (PON) architecture. In this architecture, wavelength selective switches (WSSs) are used at the remote node to improve flexibility, data security and power budget compared to other TWDM-PON variants. We map the proposed architecture to the requirements of next-generation optical access networks in a 2020 perspective. Finally, we benchmark the proposed architecture with other proposed TWDM-PON solutions.

2011 Fifth IEEE International Conference on Advanced Telecommunication Systems and Networks (ANTS), 2011

A hybrid WDM/TDM passive optical network (PON) is a promising candidate for next-generation optic... more A hybrid WDM/TDM passive optical network (PON) is a promising candidate for next-generation optical access (NGOA) solutions. Several hybrid WDM/TDM PON architectures can be designed, each with a different degree of flexibility, going from fully static, over partially flexible to fully flexible architectures. A flexible architecture can serve several advantages, like energy efficiency, network migration and network extensibility. The more flexible architectures, however, are either more expensive, experience a higher power loss or are less secure. A question that arises is if a fully flexible architecture really needed. An important assessment parameter is the number of wavelengths required at a certain network load. In this paper, we introduce and compare two different flavors of flexibility based on the multicasting and switching functionality of different architectures. By exhaustive simulation, we study the gains of different variants of flexibility with different traffic models. I.

2012 IV International Congress on Ultra Modern Telecommunications and Control Systems, 2012

Hybrid TDMA/WDM (TWDM) Passive Optical Network (PON) is a promising candidate for Next-Generation... more Hybrid TDMA/WDM (TWDM) Passive Optical Network (PON) is a promising candidate for Next-Generation PON (NG-PON) solutions. We propose end-to end reliable architectures for business users and a cost-effective network for residential users. We evaluate the proposed reliable architectures in terms of protection coverage, connection availability, impact of failure (i.e. to avoid a huge number of end users being affected by any single failure) and cost in different populated scenarios.

2013 15th International Conference on Transparent Optical Networks (ICTON), 2013

Time and wavelength division multiplexed passive optical networks (TWDM-PONs) have been widely co... more Time and wavelength division multiplexed passive optical networks (TWDM-PONs) have been widely considered as one of the next evolutionary steps of optical access networks. A variety of algorithms exists that explore the problem of scheduling and wavelength assignment in TWDM-PONs. These algorithms, however, allow unlimited switching of wavelengths. In reality, wavelength switching increases guard bands due to the tuning and the switching time of components, limiting channel utilization and increasing packet delays. We propose a novel dynamic bandwidth allocation (DBA) algorithm for TWDM-PON that minimizes the performance degradation due to excessive wavelength switching.

Journal of Optical Communications and Networking, 2013

Quality-of-service (QoS) support in Ethernet passive optical networks (EPON) is a crucial concern... more Quality-of-service (QoS) support in Ethernet passive optical networks (EPON) is a crucial concern. We propose a new dynamic bandwidth allocation (DBA) algorithm, for service differentiation that meets service level agreements (SLAs) of the users. The proposed delay aware (DA) online DBA algorithm provides constant and predictable average packet delay and reduced delay variation for the high and medium priority traffic while keeping the packet loss rate under check. We prove the effectiveness of the proposed algorithm by exhaustive simulations.

Telecommunication Systems, 2013

Different hybrid WDM/TDM PON architectures are compared in terms of flexibility, simplicity (affe... more Different hybrid WDM/TDM PON architectures are compared in terms of flexibility, simplicity (affecting the cost), insertion loss (affecting the reach) and security. Special attention is given to the flexibility aspect in next generation optical access networks by designing different architectures with a different degree of flexibility, which are able to cope with different ranges of dynamic bandwidth allocation (DBA) possibilities. This paper assesses the degree of architectural flexibility needed to deal with some important flexibility advantages. It is shown that mostly a partially flexible architecture fulfils the needs. The architectures are then further evaluated from a cost and reach perspective. In this way, we provide a complete comparison considering all the key aspects of access network design. It is shown that a hybrid WDM/TDM PON with a partially flexible architecture in the first remote node can be an interesting candidate for next-generation optical access networks.

Optics Express, 2012

The optical network unit (ONU), installed at a customer's premises, accounts for about 60% of pow... more The optical network unit (ONU), installed at a customer's premises, accounts for about 60% of power in current fiber-to-the-home (FTTH) networks. We propose a power consumption model for the ONU and evaluate the ONU power consumption in various next generation optical access (NGOA) architectures. Further, we study the impact of the power savings of the ONU in various low power modes such as power shedding, doze and sleep.

Optical Switching and Networking, 2012

For building an optical access network, we propose some new hybrid WDM/TDM passive optical networ... more For building an optical access network, we propose some new hybrid WDM/TDM passive optical network (PON) architectures that use wavelength selective switches (WSSs) at the remote node to improve flexibility, data security and power budget. Through simulations we demonstrate that the switching capabilities of a WSS can provide additional gains in terms of wavelength usage by a better statistical multiplexing. Several WSS-based hybrid WDM/TDM PON variants are proposed and assessed. These architectures are also compared with the more commonly used hybrid WDM/TDM PONs consisting of power splitters and/or arrayed wavelength gratings (AWGs), in terms of cost and power budget.

IEEE Communications Magazine, 2014

Individual users and enterprises are increasingly relying on the access to internet services and ... more Individual users and enterprises are increasingly relying on the access to internet services and cannot accept long interruption time as easily as before. Moreover, the main characteristics of next generation optical access (NGOA) networks, such as long reach and large number of users per feeder line, turn the network reliability to an important design parameter to offer uninterrupted service delivery. In this regard, protection mechanisms become one of the crucial aspects that need to be considered in the design process of access networks. On the other hand, it should be noted that not all the users can afford to pay a high extra cost for protection and hence it is important to provide resilience in a costefficient way. A passive optical network (PON) combining wavelength division multiplexing (WDM) and time division multiplexing (TDM) technologies, referred to as hybrid WDM/TDM PON or HPON, is one of the most promising candidates for NGOA networks due to its ability to serve a large number of subscribers and to offer a high capacity per user. For these reasons in this paper, we propose HPON architecture offering different degrees of resilience depending on the user profiles, i.e. partial and full protection for residential and business access, respectively. Besides, the investment cost of providing resilience for the proposed schemes is investigated considering various protection upgrade road maps. Our results confirm that protecting the shared part of network with a large number of users is required in order to keep the failure impact at an acceptable level, with less than 5% increase of the investment cost compared to the unprotected case. Meanwhile, the proposed end-to-end protection for the business users considerably reduces the risk of service interruption for this kind of demanding users without a need for duplicating the deployment cost of an unprotected connection. Furthermore, a sensitivity analysis is performed to investigate the impact of changes in business user percentage and protection upgrade time on the deployment cost. The results may be used as an advice for a costefficient deployment of reliable fiber access networks.