Michael Irizarry

License-Assisted Access Considerations

With mobility as the dominant theme in the emerging fabric of IoE (Internet of Everything), a prolific demand for capacity is a natural consequence. Throughput, latency reduction, availability and reliability are elemental attributes of experientially attractive and robust mobile multimedia services. These elemental attributes drive the demand for spectrum. The use of E-UTRA (Enhanced-Universal Terrestrial Radio Access) technologies, specified under the LTE project, over the 5 GHz unlicensed spectrum, is being considered as a forward-looking approach for standardization to meet the growing capacity demands to support mobile multimedia services. The 5 GHz spectrum band also includes the ISM (Industrial, Scientific, and Medical) band, which is utilized by the IEEE 802 family of technologies. LAA (license assisted access) refers to the use of LTE technologies over unlicensed spectrum, with assistance using a licensed radio frequency carrier. A significant challenge in the standardization of LAA for interoperability is the management of co-channel and adjacent channel interference, when both E-UTRA and the IEEE family of technologies share the same unlicensed spectrum. These challenges are compounded by the differences in the regulations across the three different global ITU (International Telecommunication Union) regions (Europe, Americas, and Asia.) This article will identify strategies and corresponding trade-offs to mitigate the coexistence challenges between the E-UTRA and the IEEE family of technologies, utilizing forward-looking and interoperable enablers. In conclusion, the article will delineate recommendations for a realization of CA (carrier aggregation) between licensed and unlicensed spectrum for downlink and uplink, to accomplish deployment-specific capacity enhancements.

Impact of Dirty Devices on CDMA Network Coverage and Capacity

The introduction of cellphones with poor receiver sensitivity, known as dirty devices, to the Code Division Multiple Access (CDMA) cellular network results in a reduction in cell edge coverage, degraded capacity, and higher drop-call rates. This poor network performance has a negative impact on customer experience and satisfaction, which may result in increased churn for CDMA wireless carriers. Previous research on the impact of dirty devices has used computer-based simulations. This paper demonstrates the influence of dirty devices on a live commercial CDMA network using two distinct approaches. The first approach deploys dirty and non-dirty devices in a live commercial cell, and measures the impact on forward base transceiver station (BTS) power and forward link Ec/Io (Ec is the received pilot chip energy and Io is the spectral density of the total power seen by the device). A series of tests on a live CDMA network with known dirty devices shows an increase in BTS transmit power resources compared with non-dirty devices, leading to the degradation of forward link Ec/Io. The second approach uses a statistical study of the aggregated pilot strength measurement messages reported by the mobile to ascertain the impact of known dirty devices on the overall network Ec/Io of non-dirty devices.

A Comparative Study of Voice Quality and Coverage for Voice over Long Term Evolution Calls Using Different Codec Mode-sets

In this paper, we examine the impact of four voice over long term evolution adaptive multi-rate wideband codec mode-sets on coverage at pedestrian and vehicular speeds. Industry-standardized mean opinion scores were used as a metric for voice quality. Controlled laboratory experiments simulating pedestrian speeds indicated that there was an improvement in voice quality when mode-set eight was employed. At vehicular speeds, mode-set eight outperformed the other mode-sets for path losses less than 130 dB; however, all four mode-sets experienced a significant decline in voice quality when the path loss was greater than 130 dB. Based on the current implementations, there are no significant benefits to lowering the mode-sets or deploying dynamic codec rate adaptation.