Badri N. Varadarajan

PRIME Interoperability Tests and Results from Field

PRIME (PoweRline Intelligent Metering Evolution) is one of the prominent upcoming powerline communication technologies, targeted for use in smart metering applications. The PRIME PHY / MAC specifications are open, publicly available and are developed by the PRIME Alliance, an industry consortium that includes utilities, meter vendors and semiconductor suppliers. PRIME employs OFDM modulation in the CENELEC A band (9 - 95 kHz), and achieves data rates from 21 kbps to 128 kbps at the PHY layer. The PRIME MAC is optimized for tree- topology networks, and features a novel node discovery and network building process. PRIME converges to IPv4 and IEC 61334-4-32 at the network layer, and is evolving to support IPv6. In this paper, we describe the PRIME Alliance, and review technical details of the PRIME PHY and MAC. We review the certification and interoperability tests defined by the PRIME Alliance, to ensure openness and future-proof technical performance with multi-vendor solutions. We present some initial results from small-scale PRIME field deployments.

Performance Analysis and Enhancements of Narrowband OFDM Powerline Communication Systems

We compare the performance of different powerline communication (PLC) systems under various realistic noise conditions, namely white noise, periodic impulsive noise in the time-domain, and narrowband co-channel interference. We base the study on narrowband (< 500 kHz) PLC based on OFDM in general, with specific focus on two prominent PLC industrial specifications for e-metering applications: PRIME and G3. From the simulation results, for white noise and for higher coding rates we find that the Reed Solomon (RS) outer code used in G3 yields significant gains, but can be improved by adapting the RS code rate to the packet size. For lower coding rates, we do not find significant advantage of adding RS coding. For time-domain impulsive noise, we find that the best performance-complexity tradeoff is obtained by choosing the interleaver size to be somewhere between one symbol (PRIME) and the entire packet (G3). Specifically, it is beneficial to choose an interleaver whose size is comparable to the AC lines period, which is the typically inter-burst duration of impulsive noise. For narrowband interference, both PRIME and G3 offer good performance, but PRIME is preferable because it achieves higher data rates by employing higher order modulation. The immunity to narrowband interference makes PRIME/G3 an attractive candidate for automotive charging applications.

Empirical measurements of the low-frequency power-line communications channel in rural North America

This paper addresses power-line communication (PLC) for automated metering infrastructure (AMI) and automated meter reading (AMR) applications in North America, with specific focus on the physical layer. FCC regulations permit powerline communication systems in the US to use the band from 9 kHz to roughly 500 kHz. This paper presents channel and noise characteristics in this band, based on field tests. It is shown that the main challenge in communicating in this band is severe signal attenuation by service transformers. In rural areas, these transformers supply eight or fewer end points on average. Consequently, it is not economical to use a bridge device across each transformer. Rather, one router is placed on the medium voltage line for every few service transformers. We consider the channel between a concentrator or a router on the medium voltage line (around 7.2 kV), and low-voltage (around 110V) end points connected to transformers some distance away on the medium voltage line. The signal-to-noise ratios observed in such a link, and implications for signal design, are studied. Data is provided on all modem connection scenarios, including medium voltage to low voltage (MV→LV), low voltage to medium voltage (LV→MV), and medium voltage to medium voltage (MV→MV). These results are intended to define requirements for a PHY / MAC communication system that can support the AMI application in such channel conditions.

PRIME on-field deployment First summary of results and discussion

PRIME (PoweRline Intelligent Metering Evolution) is a narrowband power line communications (PLC) technology targeted for use in smart metering applications. From its initial conception back in 2006, it was designed considering utility needs for a reliable, open PHY/MAC specification which could become a globally recognized industry standard. The use of OFDM techniques and well-known forward error correction mechanisms, along with novel discovery and network-building MAC procedures, allow for cost-effective, seamless integration with recognized standard metering protocols such as DLMS/COSEM. This paper presents results obtained from real-field multi-vendor deployments with PRIME-compliant interoperable implementations at Iberdrola network in Spain. The focus is on the definition of “availability rates”, how to approach a systematic testing laboratory scenario and obtained results, and sample performances measured at field locations. Finally several considerations on noise sources and impedance, coming from real experience, will be discussed.

Nested codebook design for MIMO precoders

In multi-input, multi-output (MIMO) communication systems, significant throughput gains can be obtained by closed-loop operation, where two aspects of the transmission are adapted to channel conditions: the transmission rank (number of independent spatial layers); and the precoding matrix which maps the spatial layers to the transmit antennas. To facilitate feedback and signaling, the precoding matrix for each rank is often restricted to a finite pre-determined codebook. Prior research has studied the problem of designing the codebook independently for each rank, with the aim of maximizing throughput gains for a given codebook size. In this paper, we propose to jointly design the family of codebooks for various transmission ranks. Our nested codebooks greatly simplify both codebook design and the selection of precoding matrix for a specific channel. In addition, we prove by analysis and simulation results that the complexity reduction is obtained without sacrificing throughput gains. Due to these advantages, the proposed structured codeboook design has been accepted for use in the 3GPP Long Term Evolution (LTE) standard.

Efficient Channel Quality Feedback Schemes For OFDMA Systems With Different Schedulers

In orthogonal frequency division-multiple access (OFDMA) systems, the available downlink frequency is divided into subbands which are shared among users. The transmitter determines the users that are scheduled on each subband, and the data rate for each user. To enable these transmitter choices, each user feeds back a channel quality indicator (CQI), giving a compressed version of its observed signal-to-interference-noise ratio (SINR) on all subbands. In this paper, we classify existing CQI compression schemes into symmetric and asymmetric schemes. Symmetric schemes aim to accurately represent the CQI on all subbands, and are shown to be suitable when the receiver cannot accurately predict the subbands on which it will be scheduled. This happens, for instance, when the receiver is fast-moving, or when a round- robin scheduler is employed, or during low load conditions. Asymmetric schemes, on the other hand, greedily achieve accuracy only in high-SINR subbands, and are shown to perform well in high-load cellular networks with proportional fair scheduling and low-speed users. We propose one new scheme in each category. Simulation results for a 3GPP LTE cellular network show that our proposed schemes achieve similar or better performance than the current best-M feedback scheme used in LTE, with 30% less overhead.