Adaptive Modulation and Coding AMC replaces the role of power control so that the modulation and coding rate are changed depending on the channel condition. This is accomplished by locating the scheduling algorithm for channel allocation at the Node B instead of the RNC in Release The UE monitors this channel continuously to determine when to read its data from the HS-DSCH, and the modulation scheme used on the assigned physical channel.
It is allocated to a user at 2 ms intervals. It carries no upper layer information, and therefore has no logical or transport channel mapping. The advantages and disadvantages of each approach are apparent. Whereas DCH is suited for high data traffic volumes with a maximum rate of kbps , setup time is slow, making it unsuitable and inefficient for bursty data such as a web browsing application.
By contrast, FACH has a low setup time but is a common channel without power control or other mechanisms to account for channel conditions. In addition, jitter sensitive applications may required guaranteed bandwidth. The CPCH is optional for terminals and not commonly used. The DCH is the primary means of supporting packet data services.
Macro Diversity is supported using soft handover. Data transfer can also be supported on the RACH. Because it needs to be shared among all UEs, higher data rates are generally not supported.
Macro Diversity is also not supported and the channel operates with a fixed or slow changing power allocation. Thus, from a practical point of view, the Dedicated Channel DCH is the way to accommodate packet services in a Release 99 network. However, significant limitations must also be faced when using the Uplink DCH: z Large Scheduling Delay — In Release 99, the scheduling of resources is done in the serving RNC and involves Layer 3 signaling messages to and from the UE, which causes the mechanism to be relatively slow in assigning or reconfiguring the resources assigned to a particular UE.
In addition to that, the only available mechanism for retransmissions of erroneous packets is located in RNC, thus significantly contributing to the latency figures. In order to achieve higher peak data rates, lower coding rates and multi-code transmission shall be used, but these are not available in real systems.
These grants are assigned to users by using a fast scheduling algorithm that allocates the resources on a short-term basis every tens of ms.
During periods of high activity, a given user may get a larger percentage of the available resources, while getting little or no bandwidth during periods of low activity. In case of NAK, data may be retransmitted. The grant is valid until a new grant is provided. After receiving the grant, the UE can transmit data starting at any TTI and may or may not include further requests. Data are transmitted according to the selected Transport Format, which is also signaled to the Node B..
The scheduling information is sent in-band to the Node-B. The grant is signaled to the UE by new grant channels. The grant is determined based on uplink interference situation Rise-over-Thermal noise at the Node-B receiver and on the UE transmission requests and level of satisfaction.
Data are transmitted by the UE on together with the related control information. After receiving the grant, the UE can transmit data starting at any TTI and may or may not include further scheduling information. The transport format is first selected based on the received grant, on the available power and on the data in the buffer. The Happy Bit is also included. Requires higher processing capabilities at the UE and Node B.
In a practical scenario, the practical maximum data rate will be less than 5. For 10 ms TTI, a maximum of 2 Mbps peak data rate can be achieved, corresponding to a maximum transport block size of bits. In order to achieve higher rates, a TTI of 2 ms shall be used. For details see TS Up to 4 channels can be used to carry the E-DCH transport channel in a multi-code transmission scheme.
The absolute grant indicates directly to the UE the Traffic-to-Pilot ratio that shall be used for scheduled transmissions. The relative grant tells the UE to increase, decrease, or maintain the current Traffic-to-Pilot ratio.
They carry no upper layer information, and therefore have no logical or transport channel mapping. Concepts of MIMO can be incorporated to achieve higher cell capacity. Higher order modulation schemes will benefit users of these technologies in good geometry conditions.
HSDPA is a shared channel and scheduling of user data is driven by availability of data. The question, then, is why not use application behavior to drive transmission of DL and UL channels?
This can reduce UE battery consumption and interference. F-DPCH design can be enhanced to improve efficiency. The FACH transport channel is shared by all the users in a cell. A wireless communication system utilizing multiple transmit antennas and multiple receive antennas over the wireless channel is often referred to as a MIMO system.
In a MIMO system, there are N x M signal paths from the transmit antennas and the receive antennas, and the signals on these paths are not identical. On the transmitter end, the data signal is constructed in such a way that different antennas carry different variations of the signal, such as different phases, amplitudes, or waveforms. At the receiver end, each variation of the data signal is received differently at different antennas due to differences in channel fading.
From an implementation perspective, the MIMO system can be categorized as a closed-loop system or an open-loop system. In a closed-loop system, the receiver reports the channel information to the transmitter.
In an open-loop system, such information is not available at the transmitter. This course focuses only on the closed-loop MIMO system. Stronger pipes have less interference than the weaker pipe. Hence, it makes sense to spend more power on the stronger pipes because the power will be more efficiently utilized carrying data instead of combating interference. The data throughput gain achieved when all the power is focused on the strongest pipe is referred to as the Array gain.
When the overall channel condition is good and all the pipes are strong, it makes sense to multiplex data transmission on all the pipes. Multiplexing gain also referred to as spatial multiplexing gain increases the benefit of MIMO far beyond what can be achieved by beamforming.
By utilizing the rich multipath and large delay spread of the fading channel, MIMO transmits independent data streams over multiple data pipes to increase throughput. The transmission power is shared among the data pipes.
Multiple antennas at both ends of the radio link are required. Channel knowledge at the transmitter is also required. Multiplexing gain does not require additional spectral bandwidth or power. In addition to beamforming or spatial multiplexing, there are many other ways to utilize the parallel data pipes created by the MIMO system. For instance, the same data stream can be transmitted on multiple data pipes, which can increase the reliability of the transmission; the gain is referred to as the MIMO diversity gain.
Or a MIMO system can transmit different data streams to different users on different pipes. Since the pipes are orthogonal, the interference between the users, also referred to as the co-channel interference, is reduced. This increases system capacity. Depending on the channel condition, the system can dynamically change MIMO operating mode to best utilize the array gain and multiplexing gain.
Is this content inappropriate? Report this Document. Flag for inappropriate content. Download now. Related titles. Carousel Previous Carousel Next. Adding Support for Authentication and Encryption to Openbts. Jump to Page. Search inside document. Szu-Ying Chen Algorithm Integ. Mohammed Tahseen Shaikh. Mahmoud Anshasi. Leow Chun Fung. Ritu Jain. Ejaz Ahmad. Syed Muhammad Kamran. Eyad Mostafa. Halo Hehe. Sukrit Chaudhary. Franco Cortez. Abdul Majeed Khan.
Jump to Page. Search inside document. Europe China Japan Korea North America Assigning a non IMT spectrum would result in higher handset prices for 3G systems complex circuitry to support international roaming across different frequency bands. This service is based on the characteristics of the radio interface and is maintained for a moving user equipment A bearer service includes all aspects to enable the provision of a contracted QoS.
RNC manages the QoS requirements. In a WCDMA transmitter, neither time nor frequency is used to separate different users, but codes in an operation known as spreading. The power density of the spectrum is decreased several times and the transfer of information is still possible even below background noise. CDMA is very spectrum efficient due to the possibility of reusing each carrier in each cell.
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