Michael Stübert Berger

Cloud RAN for Mobile Networks—A Technology Overview

Cloud Radio Access Network (C-RAN) is a novel mobile network architecture which can address a number of challenges the operators face while trying to support growing end-users needs. The main idea behind C-RAN is to pool the Baseband Units (BBUs) from multiple base stations into centralized BBU Pool for statistical multiplexing gain, while shifting the burden to the high-speed wireline transmission of In-phase and Quadrature (IQ) data. C-RAN enables energy efficient network operation and possible cost savings on baseband resources. Furthermore, it improves network capacity by performing load balancing and cooperative processing of signals originating from several base stations. This paper surveys the state-of-the-art literature on C-RAN. It can serve as a starting point for anyone willing to understand C-RAN architecture and advance the research on C-RAN.

Towards converged 5G mobile networks-challenges and current trends

With the rapid development of wireless technologies, the concept of the Fifth Generation (5G) wireless communication system started to emerge and it is foreseen that it will be a result of standards convergence. The expectations towards 5G are set much higher in terms of capacity and maximum throughput when compared with Fourth Generation (4G). There are also some new technical challenges the system will need to face, like Machine to Machine (M2M) communication, energy efficiency, complete ubiquity and autonomous management. This paper analyses new technologies that could enable 5G networking, discusses potential standardisation and development directions, and presents recent research efforts in the area of future mobile networks.

Enhanced first-in-first-out-based round-robin multicast scheduling algorithm for input-queued switches

This study focuses on the multicast scheduling for M×N input-queued switches. An enhanced first-in-first-out -based round-robin multicast scheduling algorithm is proposed with a function of searching deeper into queues to reduce the head-of-line (HOL) blocking problem and thereby the multicast latency. Fan-out information of each input cell composes a traffic matrix and the scheduler executes a round-robin algorithm on each column independently. Scheduling decisions result in a decision matrix for the scheduler to release multicast cells accordingly. A matrix operation called sync is carried out on the decision matrix to reduce the number of transmission for each cell. To reduce the HOL blocking problem, a complement matrix is constructed based on the traffic matrix and the decision matrix, and a process of searching deeper into the queues is carried out to find cells that can be sent to the idle outputs. Simulation results show that the proposed function of searching deeper into the queues can alleviate the HOL blocking and as a result reduce the multicast latency significantly. Under both balanced and unbalanced multicast traffic, the proposed algorithm is able to maintain a stable throughput.

Delivering 100% throughput in a buffered crossbar with round robin scheduling

Buffered crossbars with virtual output queuing are considered an alternative to bufferless crossbars mainly because the latter requires a complex global scheduling algorithm that matches input with output. Buffered crossbars require only simple schedulers that operate independently for each output crosspoint queue column and independently for each port card. In this paper, fluid-model techniques will be utilized to show that the necessary and sufficient speedup for a NxN buffered crossbar with 1-cell crosspoint buffers is 2-1/N to deliver 100% throughput. Round robin scheduling is assumed, both among virtual output queues in port cards and among crosspoint buffers in output columns

Optical Synchronization of a 10-G Ethernet Packet and Time-Division Multiplexing to a 50-Gb/s Signal Using an Optical Time Lens

A 10-G Ethernet packet with maximum packet size of 1518 bytes is synchronized to a master clock with 200-kHz frequency offset using a time lens. The input 10-Gb/s nonreturn-to-zero packet is at the same time converted into a return-to-zero (RZ) packet with a pulsewidth of 10 ps and then time-division multiplexed with four 10-Gb/s optical time-division-multiplexing (OTDM) channels, thus constituting a 50-Gb/s OTDM serial signal. Error-free performances of the synchronized RZ packet and demultiplexed packet from the aggregated 50-Gb/s OTDM signal are achieved.

Protection for MPLS-TP multicast services

This paper proposes three innovative point-to-multipoint protection schemes to provide efficient and reliable MPLS Transport Profile multicast services, which is particularly relevant for the fast growing IPTV broadcast service. The three proposed protection schemes are all based on the interconnected rings structure, which is a widely deployed topology of legacy networks and has the natural ability to support resiliency. The first protection scheme extends the protection methods defined in the latest IETF draft standard to the interconnected rings structure. The second protection scheme introduces an adapted OAM function, which has the ability to monitor the multicast services status, such as configuration failures, software failures and performance degradation, to ensure the reliability of the whole branches and leaves of the multicast service. Furthermore, the interconnecting nodes of the rings make the protection switching decision, which releases the work to upgrade every node on the existing ring and thereby eases the MPLS Transport Profile network deployment. Instead of having one working path in one direction and the other direction being used as protection path, in the third protection scheme, the paths in both directions are used as working paths. When there is a failure, the two working paths protect each other, which increases the efficiency of the network resources. The traffic distribution on the ring is divided by these two separated working paths, which lowers the amount of affected entities when a failure occurs.

Multi-Level Round-Robin Multicast Scheduling with Look-Ahead Mechanism

In this paper, we propose a multi-level round-robin multicast scheduling (MLRRMS) algorithm with look-ahead (LA) mechanism for N×N input-queued switches. Fan-out splitting is applied, where a multicast cell can be transferred to all its destinations over any number of cell times. The scheduler constructs the Traffic Matrix before each cell transmission based on the fan-out vectors of the cells in the queues. A scheduling pointer independently moves on each column of the Traffic Matrix in a round-robin fashion and returns the decision to the Decision Matrix. The sync procedure is carried out to reduce the unnecessary transmissions of a cell. The look-ahead mechanism is executed to reduce the head-of-line blocking problem resulting in increased the throughput and reduced cell delay.

TCAM-based high speed Longest prefix matching with fast incremental table updates

This paper presents a new TCAM-based method for determining the Longest Prefix Match (LPM) in an IP routing table. The method is based on modifying the address encoder of the standard TCAM design to take the prefix lengths of the IP routing entries into account while performing multi-match resolution, thus allowing prefixes to be inserted in any random order. This enables full utilization of the TCAM address space while greatly simplifying the updating procedure as complex software sorting algorithms and extensive table modifications are avoided. The result is faster table updates and consequently a higher throughput of the network search engine, since the TCAM down time caused by incremental updates is eliminated. The LPM scheme is described in HDL for FPGA implementation and compared to an existing scheme for customized CAM circuits. The paper shows that the proposed scheme can process more packets per second, has less per-lookup power consumption and is easier to expand to larger routing tables than the existing implementation. The latency of the LPM operation is only log2 N clock cycles, where N is the maximum number of prefixes in the TCAM, and in a pipelined implementation the throughput of the system is one Longest Prefix Match lookup per clock cycle.

Flow-Based End-to-End OAM Functions for the Multicast Service on the MPLS-TP Ring Network

In order to provide a reliable multicast service on the MPLS Transport Profile ring structure network, this paper proposes two innovative schemes. The proposed multicast service scheme is designed for the multi-ring structure, which enhances the ring structures applicability and gives more support for the network resilience. The flow-based end-to-end OAM function is operated independently for each multicast traffic flow. It is able to monitor the status and performance of the whole multicast Label Switching Path and is designed in a hierarchical way on the multi-ring structure, which avoids the overwhelming burden falling on the Ingress node.

A framework for joint optical-wireless resource management in multi-RAT, heterogeneous mobile networks

Mobile networks are constantly evolving: new Radio Access Technologies (RATs) are being introduced, and backhaul architectures like Cloud-RAN (C-RAN) and distributed base stations are being proposed. Furthermore, small cells are being deployed to enhance network capacity. The end-users wish to be always connected to a high-quality service (high bit rates, low latency), thus causing a very complex network control task from an operators point of view. We thus propose a framework allowing joint overall network resource management. This scheme covers different types of network heterogeneity (multi-RAT, multi-layer, multi-architecture) by introducing a novel, hierarchical approach to network resource management. Self-Organizing Networks (SON) and cognitive network behaviors are covered as well as more traditional mobile network features. The framework is applicable to all phases of network operation like planning, deployment, operation, maintenance and therefore aids network operators in improving their business potential.