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Communications, IEE Proceedings-

Issue 5 • Date Oct. 2006

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Displaying Results 1 - 25 of 29
  • New linear codes derived from binary cyclic codes of length 151

    Publication Year: 2006 , Page(s): 581 - 585
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (174 KB)  

    The minimum distance of all binary cyclic codes of length 151 is determined. Almost all of these cyclic codes have the same parameters as the best linear codes given in Brouwer's database. A nested chain of linear codes is derived from these cyclic codes and some new binary codes are obtained by applying Constructions X and XX to pairs of codes in this chain. Good candidates for nested codes can also be obtained by enlarging the cyclic codes of high minimum distance. In total, there are 39 new binary linear codes that have a minimum distance higher than codes previously considered to be the best linear codes View full abstract»

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  • Improved performance SOVA turbo decoder

    Publication Year: 2006 , Page(s): 586 - 590
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (185 KB)  

    A novel approach for improving the performance of the soft-output Viterbi algorithm (SOVA) when applied to turbo decoding is proposed. Based upon a modified two-step scaling factor approach for the decoder's extrinsic information, it is shown that the proposed technique reduces significantly the error floor present in previous SOVA-based turbo decoding techniques. Various computer simulated bit error rate (BER) performance evaluation results for binary phase shift keying (BPSK) signals transmitted over the additive white Gaussian noise (AWGN) and flat Rician fading channels clearly indicate that for large interleaver sizes and high numbers of decoding iterations no error floor is observed for BERs as low as 10-6 View full abstract»

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  • Geometric augmented product codes

    Publication Year: 2006 , Page(s): 591 - 596
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (345 KB)  

    We propose a new simple decomposable code construction technique that generates codes with the full information rate for all of the minimum Hamming distance-4 binary linear block codes of even length greater than or equal to eight. Additionally, some optimal Hamming distance-8 and higher distance codes are obtained with our proposed scheme. A generic trellis structure for the proposed codes was also designed. It is shown that our trellis structures provide lower decoding complexity in comparison to the trellises of some other well-known block codes View full abstract»

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  • Hybrid list decoding and Kaneko algorithm of Reed-Solomon codes

    Publication Year: 2006 , Page(s): 597 - 602
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (261 KB)  

    The authors present a hybrid list decoding and Kaneko algorithm for Reed-Solomon (RS) codes. A new ruling out scheme motivated from Takuya Koumoto's work for a reduced-complexity list decoding algorithm, which reduces the complexity of the hybrid algorithm, is also proposed. Simulation results show that the performance of the hybrid algorithm for both (15, 7) and (31, 21) RS codes is comparable with the hybrid algorithm which combines the list algorithm and the Chase algorithm. But the complexity of the proposed hybrid algorithm is much less than that of the hybrid algorithm which combines the list algorithm and the Chase algorithm at high signal-to-noise ratios View full abstract»

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  • Asymmetric rate compatible turbo codes in hybrid automatic repeat request schemes

    Publication Year: 2006 , Page(s): 603 - 610
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (321 KB)  

    The authors present asymmetric turbo hybrid automatic-repeat-request (ATH-ARQ) schemes that employ component code selection and asymmetric rate compatible punctured turbo codes (ARCPT) for enhanced performance in fading channels. The paper also presents a novel low-rate ARCPT encoder structure. An analysis is presented for efficient ARCPT puncture schemes for improved throughput performance at low and high SNR values. It is shown that in certain instances, the use of conventional turbo code structures results in the best performance View full abstract»

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  • ARQ scheme with adaptive block size for bidirectional wireless endoscopy system

    Publication Year: 2006 , Page(s): 611 - 618
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (662 KB)  

    By analysing the characteristics of the communication channel in a bidirectional digital wireless endoscopy system, the authors propose an efficient automatic repeat query (ARQ) scheme, with a dynamically adaptive block size, a high data rate and an ultra-short communication distance. Two new strategies for adaptive block-size decision are also proposed. The optimum block-size formula for the wireless endoscopy system is given and analysed in detail. This ARQ scheme ensures not only the image's communication quality at a high data rate (2 Mbit/s) but also the optimum communication-power efficiency in the capsule View full abstract»

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  • Multi-interval line coding technique for high speed transmissions

    Publication Year: 2006 , Page(s): 619 - 625
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (438 KB)  

    A multi-interval line coding (MILC) technique which operates over blocks of intervals is proposed to increase the transmission rate without expanding the bandwidth or using higher order signalling. This is done by dividing every interval into sub-intervals, and allowing the signals to make amplitude transitions at the end of sub-intervals. However, the waveforms are generated by maintaining the duration of all individual pulses at least at equal to the original bit interval thereby maintaining spectral variations close to that of ordinary binary signals. Numerical results presented for data transmission over a printed circuit board (PCB) trace indicate that MILC schemes perform significantly better than ordinary binary signalling at the same information transfer rate under severe ISI conditions View full abstract»

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  • Tight lower bounds on the symbol error rate of uncoded nonuniform signalling over AWGN channel

    Publication Year: 2006 , Page(s): 626 - 632
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (216 KB)  

    New Bonferroni-type lower bounds on the word error probability of uncoded systems are developed. The new family of bounds is based on a recent Bonferroni inequality proposed by Cohen and Merhav. These novel tight bounds are developed for optimal maximum a posteriori (MAP) coherent detectors with nonuniform signalling over additive white Gaussian noise channel. The results are compared to the state-of-the-art KAT lower bounds and it is shown that the superiority of one bound to another is dependent on the signal constellation, the amount of nonuniformity of the Bernoulli source to be communicated, and the SNR range of interest. For instance, for smaller deviations from the uniform case, which are in fact more plausible, and at low SNRs, the new bounds are tighter than KAT lower bounds for all the constellations studied View full abstract»

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  • Time domain implementation of space-time/frequency block codes for OFDM systems

    Publication Year: 2006 , Page(s): 633 - 638
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (195 KB)  

    Spatial diversity is a widely applied technique for enhancing the wireless system performance, since it greatly reduces the detrimental effects of multipath fading. Orthogonal space-time block codes are considered to be a good choice for spatial diversity, as they provide full diversity without any channel state information at the transmitter. The standard frequency domain application of these block codes for OFDM-based systems requires multiple inverse fast Fourier transform operations per OFDM symbol. This increases the system computational load, which grows with the increasing number of transmit antennas and sub-carriers. By using well-known properties of the discrete Fourier transform, we propose a time domain encoding of these codes, thereby requiring only one transformation per OFDM symbol. The proposed encoding strategy significantly reduces the computational load and hence facilitates implementation View full abstract»

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  • GDH group-based signature scheme with linkability

    Publication Year: 2006 , Page(s): 639 - 644
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (182 KB)  

    Recently, a linkable ring signature scheme (called the LWW signature scheme), exhibiting the properties of anonymity, linkability and spontaneity, was presented. Its security is based on the decision Diffie-Hellman (DDH) problem. The distinguishing feature of the LWW signature scheme that differentiates it from other ring signature schemes is linkability, i.e. two signatures by the same signer can be linked. The LWW scheme can be used to construct new efficient e-voting systems. The drawback of the LWW scheme is that it works well on a group where the DDH problem is hard, but does not work on a GDH group where the DDH problem is easy and the computational Diffie-Hellman (CDH) problem is hard. In this paper, a linkable ring signature scheme is presented, based on a GDH group with anonymity, linkability and spontaneity. The security of the scheme is reduced to the discrete logarithm and a new intractability assumption (called DPDH problem) under the random oracle model View full abstract»

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  • Low complexity LMMSE channel estimation for OFDM

    Publication Year: 2006 , Page(s): 645 - 650
    Cited by:  Papers (4)
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (357 KB)  

    The authors propose low complexity versions of a linear minimum mean square error (LMMSE) channel estimator for orthogonal frequency division multiplexing (OFDM) systems. They partition the channel autocorrelation matrix in the LMMSE estimator into small sub-matrices. The size of sub-matrix is determined by channel coherence bandwidth, a range of highly correlated channel frequency responses. Since the proposed estimator uses small sub-matrices instead of the whole channel auto-correlation matrix, the complexity is significantly reduced in spite of slight performance degradation. The performance of mean square error (MSE) has been evaluated in an exponential decay channel model through computer simulation to verify the validities of proposed schemes View full abstract»

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  • Estimating errors in transmission systems due to impulse noise

    Publication Year: 2006 , Page(s): 651 - 656
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (224 KB)  

    Impulse noise is a major limiting factor to the performance of digital subscriber lines, powerline communication systems, and digital TV. Research has shown that the impulse noise in all those transmission media has very similar statistical properties. Using noise distribution parameters for the specific case of telephone lines, this paper suggests a Bernoulli-Weibull model of impulse noise in the local loop at symbol level. This model is then applied to develop closed-form expressions for the error probability of PAM and single carrier QAM. A novel extension of the distribution of the impulse noise amplitudes to two dimensions is introduced to enable the analysis of two-dimensional modulations, such as QAM. It is shown that earlier noise models, which assume Gaussian distributed impulse amplitudes or Rayleigh distributed powers, produce overly optimistic results for the errors owing to impulse noise in comparison with the Bernoulli-Weibull model presented here. The error performance of multicarrier QAM (DMT) is also evaluated based on the Bernoulli-Weibull model, however this is done numerically owing to the lack of an analytical solution. It is shown that multicarrier QAM performs better than single carrier systems but only for low impulse power and low impulse probability. The analytical framework presented here is also directly applicable to powerline transmission and DVB-T systems as they have very similar impulse noise statistics to those in telephone lines View full abstract»

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  • Adaptive channel aided decision feedback equalisation for SISO and MIMO systems

    Publication Year: 2006 , Page(s): 657 - 663
    Cited by:  Papers (2)
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (280 KB)  

    Error propagation can seriously affect the performance of an adaptive decision feedback equaliser (DFE), especially when operated in time-varying channel environments. Error propagation not only affects DFE decisions, but also disturbs the DFE adaptation. The paper focuses on improving the robustness against error propagation for the least-mean-square (LMS) based minimum mean-squared-error DFE (MMSE-DFE). A specifically designed channel estimator is introduced to help the DFE adaptation in the decision-directed (DD) mode. Unlike the conventional DFE, the proposed adaptive channel-aided DFE (ACA-DFE) only adapts the feedforward filter with the LMS algorithm. The feedback filter, however, is obtained from the postcursors of the estimated channel convolved with the feedforward filter. As a result, the proposed ACA-DFE can reduce the error propagation effect and perform better than the conventional adaptive DFE. We also demonstrate that the ACA-DFE can be extended to multiple-input multiple-out (MIMO) systems improving the performance of the conventional MIMO DFE View full abstract»

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  • Constant hardware delay in integrated switching elements with multiserver output queues

    Publication Year: 2006 , Page(s): 664 - 670
    Cited by:  Papers (1)
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (330 KB)  

    The authors consider an integrated switching element with a shared buffer memory and a constant hardware delay. This hardware delay is caused by the hardware operations required to process the routing information of incoming cells. A general uncorrelated cell arrival process in the switch, an independent and uniform routing process of cells from the inlets to the outlets of the switch and a first-come-first-served queueing discipline are assumed. The performance of the switching element is evaluated by means of an analytical technique based on an extensive use of probability generating functions. Explicit expressions for the probability generating functions, the mean values, the variances and the tail probabilities of the occupancy and the cell delay of the switch are obtained. Numerical examples show that the hardware delay has an important impact on the switch performance. View full abstract»

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  • Fast bandwidth-constrained shortest path routing algorithm

    Publication Year: 2006 , Page(s): 671 - 674
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (141 KB)  

    QoS routing has been a critical issue for providing QoS in high-speed networks. The authors present the design of a fast routing algorithm for selecting the shortest path connecting a pair of nodes subject to a bandwidth constraint. The algorithm works by combining the strategies of informed search and backwards routing. Its worst-case computational complexity is deduced to be O(|E|lg|V|), where |E| and |V| represent the number of links and nodes in the network, respectively. Simulation results indicate, however, that the designed algorithm can greatly reduce the average-case running time in computing such constrained shortest paths as compared with existing work View full abstract»

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  • Effective congestion control for QoS enhancement of self-similar multimedia traffic

    Publication Year: 2006 , Page(s): 675 - 682
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (735 KB)  

    Owing to the existence of noticeable concentrated periods of contention and idleness, self-similar traffic can greatly increase packet delay and loss probability and thus reduce system resource utilisation. The development of efficient congestion control mechanisms plays a central role in the improvement of network quality of service (QoS), in particular for real-time multimedia applications. By exploiting the property of scale-invariant burstiness and correlation inherent in self-similar traffic, the authors propose an effective congestion control scheme, named adaptive wavelet and probability-based scheme (AWP), which concurrently operates over multiple time scales. AWP adopts the extended multifractal wavelet model (EMWM) for analysing estimated traffic volume across multiple time scales. Furthermore, a new auto-correction algorithm based on Bayes' theory for confidence analysis is employed to examine the validity of the predicted information. The analysis results can be used to enhance the adaptability of the prediction algorithm. In particular, the AWP framework can be easily extended to more than two time scales by increasing the level of wavelet transforms, which brings AWP a natural advantage in implementation and scalability. A series of simulation experiments have demonstrated that the proposed AWP scheme is superior to TCP and TFRC as it can greatly improve the QoS of multimedia data transmission while avoiding congestion collapse on the network. View full abstract»

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  • Traffic characteristics of aggregated module downloads for mobile terminal reconfiguration

    Publication Year: 2006 , Page(s): 683 - 690
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (997 KB)  

    In recent years, there has been an increasing proliferation of reasons for software/firmware in desktop computers to be upgraded over the Internet, and as computational devices continue to become ever more advanced and compact, it is anticipated that the same will be the case for mobile terminals in the near future. In this paper, we consider some important characteristics of such upgrade traffic. Initially, we study file size distributions for various file types on a range of servers/systems, and conclude that the Pareto distribution, as is often used to represent file sizes, is inappropriate. In fact, in order to achieve a better fit to the bulk of the distribution while still maintaining an infinite variance, file sizes are usually far better represented by the Pareto type 2 (Lomax) distribution. Leading on from this, we simulate multiple concurrent files being downloaded over a bottleneck link, taken from particular file-size distributions with a focus on mobile terminal reconfiguration. In doing so, we investigate the degree of burstiness/self-similarity and correlation structure in the resulting traffic. Understanding these phenomena is particularly important because of their tendencies to increase packet losses and queuing delays through compound fluctuations in link loads View full abstract»

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  • End-point synchronisation and handover for multi-homed services

    Publication Year: 2006 , Page(s): 691 - 696
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (378 KB)  

    It is proposed to implement a synchronised routing table at the transport layer, referred to as an association routing table (ART), to improve the performance of multi-homed transport protocols. An algorithm is described that ensures that the routing tables can be synchronised, which is then used to implement a handover mechanism. The ART is implemented within the stream control transmission protocol (SCTP). It is shown that by using a synchronised ART, it is possible to implement failover in cases where the standard SCTP cannot do so, Configurations are more resilient to network errors, and it is possible to perform a handover without any network support View full abstract»

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  • Performance analysis of an improved power-saving medium access protocol for IEEE 802.11 point coordination function WLAN

    Publication Year: 2006 , Page(s): 697 - 704
    Cited by:  Papers (1)
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (276 KB)  

    Wireless enabled portable devices must operate with the highest possible energy efficiency while still maintaining a minimum level and quality of service to meet the user's expectations. The authors analyse the performance of a new pointer-based medium access control protocol that was designed to significantly improve the energy efficiency of user terminals in wireless local area networks. The new protocol, pointer controlled slot allocation and resynchronisation protocol (PCSAR), is based on the existing IEEE 802.11 point coordination function (PCF) standard. PCSAR reduces energy consumption by removing the need for power saving stations to remain awake and listen to the channel. Using OPNET, simulations were performed under symmetric channel loading conditions to compare the performance of PCSAR with the infrastructure power saving mode of IEEE 802.11, PCF-PS. The simulation results demonstrate a significant improvement in energy efficiency without significant reduction in performance when using PCSAR. For a wireless network consisting of an access point and 8 stations in power saving mode, the energy saving was up to 31% while using PCSAR instead of PCF-PS, depending upon frame error rate and load. The results also show that PCSAR offers significantly reduced uplink access delay over PCF-PS while modestly improving uplink throughput. View full abstract»

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  • Performance analysis and comparisons of different ultra-wideband multiple access modulation schemes

    Publication Year: 2006 , Page(s): 705 - 718
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (361 KB)  

    The multiuser performance of two kinds of ultra-wideband (UWB) systems, namely, multi-carrier frequency-hopping-UWB and time-hopping-UWB, is evaluated. We derive the bit error rate of these systems in both AWGN and fading channels. Our numerical results show that the TH-UWB system always outperforms the MC-FH-UWB system with non-coherent detection. However, the MC-FH-UWB system with coherent detection presents a better performance than TH-UWB in a very few cases. Then, we use a practical low-rate convolutional error correcting code, which does not require any extra bandwidth further than that needed by the uncoded scheme, to improve the system performance. The results show that the coded scheme significantly outperforms the uncoded scheme in both AWGN and fading channels. Furthermore, the results indicate that, like in the uncoded scheme, in the coded scheme the TH-UWB system performs better than the MC-FH-UWB system View full abstract»

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  • Adaptive MLSD receiver employing noise correlation

    Publication Year: 2006 , Page(s): 719 - 724
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (507 KB)  

    A per-survivor processing (PSP) maximum likelihood sequence detection (MLSD) receiver is developed for a fast time-varying frequency-selective Rayleigh fading channel with coloured additive noise, which follows an autoregressive (AR) model with unknown parameters. The correlation between noise samples is exploited to considerably enhance the performance of the communications. The maximum likelihood criterion is employed based on unknown noise parameters. This criterion has some desired properties, e.g. it has a unique joint minimum at the true values of the channel and the noise parameters. The new PSP-MLSD algorithm detects the input data and jointly estimates the noise and the channel parameters all together. The proposed structure can be viewed as a traditional PSP-MLSD receiver combined with an adaptive whitening filter. In a coloured noise environment, this scheme offers a faster tracking property, more accurate estimation of the channel and a substantially lower error probability compared with the traditional PSP-MLSD structure. The signal-to-noise ratio (SNR) improvement achieved by the proposed receiver, which can be called the noise whitening gain (NWG), is almost equal to the ratio of the energy of the additive noise to the energy of the unpredictable noise component. The square of the NWG gives also an accurate approximation for the bit error rate (BER) improvement ratio obtained by using the proposed algorithm compared with the traditional one View full abstract»

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  • Asymptotic spectral efficiency of MC-CDMA with multiple antennas

    Publication Year: 2006 , Page(s): 725 - 732
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (231 KB)  

    The asymptotic spectral efficiency of multicarrier CDMA (MC-CDMA) with multiple transmit and receive antennas is analysed in this paper. The closed-form spectral efficiency is derived when matched filter and minimum mean square error (MMSE) front ends are employed. We consider the effect of the number of transmit and receive antennas on the performance of spectral efficiency. The spectral efficiency can be improved by choosing an appropriate loading factor and number of antennas in the transmitter and receiver. We also compare the spectral efficiency of MC-CDMA with that of SC-CDMA (single-carrier CDMA) View full abstract»

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  • Blind multiuser receiver for DS-CDMA wireless system

    Publication Year: 2006 , Page(s): 733 - 739
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (303 KB)  

    We consider blind signal detection in an asynchronous code-division multiple-access (CDMA) system employing short spreading sequences in the presence of unknown multipath fading. This approach is capable of countering the presence of multiple-access interference (MAI) in CDMA fading channels. The proposed blind multiuser detector is based on an independent component analysis (ICA) to mitigate both MAI and noise. This algorithm has been utilised in blind source separation (BSS) of unknown sources from their mixtures. It can also be used for estimating the basis vectors of BSS. The aim is to include an ICA algorithm within a wireless receiver in order to reduce the level of interference in wideband systems. This blind multiuser detector requires no training sequence compared with the conventional multiuser detection receiver. The proposed ICA blind multiuser detector is made robust with respect to knowledge of signature waveforms and the timing of the user of interest. Several experiments are performed in order to verify the validity of the proposed ICA algorithm View full abstract»

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  • Generation and upper bound of one-coincidence sequences in frequency-hopping multiple-access systems

    Publication Year: 2006 , Page(s): 740 - 745
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (205 KB)  

    In frequency-hopping one-coincidence sequences, a specified distance between two adjacent symbols is usually employed to reduce the interference among sequences. We propose a new algorithm to construct one-coincidence sequence sets satisfying distance constraints. Compared to the conventional method, our approach provides a more flexible and general way to generate one-coincidence sequences of variable lengths. We also obtain a tighter upper bound for one-coincidence sequences of odd length, which is independent of code lengths View full abstract»

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  • Single-carrier and multi-carrier space-time block coded transmissions over doubly selective fading channels

    Publication Year: 2006 , Page(s): 746 - 754
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (383 KB)  

    We propose a multi-stage successive interference cancellation (SIC) receiver for arbitrary linear space-time block codes (STBCs) over general time-frequency selective fading channels with single-carrier (SC) transmissions. The proposed receiver adopts the SIC approach to handle inter-symbol interference (ISI) owing to multipath propagation. Simulation results show that the proposed receiver outperforms the OFDM system after a few iterations in the BER range 10-3 to 10-5. We also propose a diversity enhancement space-time signalling scheme for four transmit antennas with an increased diversity order. Simulation results show that the proposed diversity enhancement scheme outperforms the OFDM system even at the first iteration View full abstract»

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