1 x Evolution Data Optimized Revision A (EV-DO Rev A) is a revision of the EV-DO specification. Revision A of the specification defines several physical subtypes. They are:

Subtype 0

Identical to the physical layer used in EV-DO Rev 0.

Subtype 1

Defines an enhanced access channel.

Subtype 2

The reverse link has the enhanced access channel used in subtype 1, and defines an enhanced reverse traffic channel. The forward link defines a modified traffic/control channel and an enhanced set of MAC channels.

EV-DO Revision A Reverse (Uplink) Channels

The reverse link has two physical channels: the Reverse Access Channel and the Reverse Traffic Channel.

Reverse Access Channel

The Reverse Access Channel is used by the access terminal to initiate communication with the access network or to respond to an access-terminal-directed message. The Access Channel consists of a Pilot Channel and a Data Channel as shown in the following figure. RFmx Waveform Creator does not implement any of the encoding, interleaving or repetition functions contained within the gray area.

An Access transmission consists of a preamble followed by one or more physical layer packets. Physical subtype 0 specifies that the preamble must be an integer number of frames in length, whereas physical subtypes 1 and 2 allow the preamble length to be specified in slots.

During the preamble, only the Pilot Channel is transmitted. During the access packet, both the Data Channel and the Pilot Channel are transmitted. The output power of the Pilot Channel is larger during the preamble transmission than in the access packet.

In the original EV-DO specification, data is transmitted at a fixed rate of 9.6 kbps. The enhanced access channel used in subtypes 1 and 2 lets data be transmitted at a rate of 9.6, 19.2 or 38.4 kbps. The data rate is controlled by varying the number of times the bits in a packet are repeated. RFmx Waveform Creator does not implement repetition and therefore does not provide a means of setting the data rate.

Physical subtype 0 specifies that the total power during the preamble is the same as it is during the data portion of the transmission. Physical subtypes 1 and 2 specify that the output power of the preamble is independent of the data rate and is set equal to that of the data portion transmitted at 9.6 kbps (as in subtype 0). If the data is not transmitted at 9.6 kbps, the power level during the data period may be different to the power level during the preamble period. When physical subtype 1 or 2 is selected, RFmx Waveform Creator lets you set the power during the data period relative to the power during the preamble period.

Fig. 5-17 Reverse Channel structure for the Access Channel

Reverse Traffic Channel

The Reverse Traffic Channel is used by the access terminal to transmit user-specific data to the network. The Reverse Traffic Channel consists of several channels. These are:

  1. Pilot Channel

    In physical subtypes 0 and 1 the pilot symbols and reverse rate indicator (RRI) symbols are time domain multiplexed onto the same Walsh channel, whereas in physical subtype 2, pilot and RRI symbols are transmitted on two separate Walsh channels.

  2. RRI Channel

    The Reverse Rate Indicator is used by the access terminal to indicate the rate at which the Data Channel is transmitted. RFmx Waveform Creator internally calculates the RRI symbols using the payload transmitted on the Data Channel. In addition to indicating the rate at which the data is being transmitted, the subtype 2 RRI channel transmits a 2-bit symbol indicating the subpacket index of the slot being transmitted.

  3. Auxiliary Pilot Channel

    The Auxiliary Pilot Channel is only used with physical subtype 2. The purpose of the auxiliary pilot is to provide an additional phase reference. It is used as an alternative to increasing the power transmitted on the pilot (which would cause the power on the other channels to increase).

  4. DRC Channel

    The Data Rate Control Channel is used by the access terminal to indicate to the network the selected serving sector and the requested data rate on the Forward Traffic Channel.

  5. DSC Channel

    The Data Source Control Channel is used by the access terminal to indicate to the network the selected serving cell on the Forward Traffic Channel. The DSC channel is only used in subtype 2 and is time domain multiplexed with the ACK channel.

  6. ACK Channel

    The ACK Channel is used by the access terminal to inform the access network whether a physical layer packet transmitted on the Forward Traffic Channel has been received successfully or not. Subtypes 0 and 1 specify a ‘0’ bit is transmitted if a packet has been successfully received; otherwise a ‘1’ is transmitted. Subtype 2 specifies that when acknowledging a single-user packet, a ‘1’ is transmitted to signify an ACK and a ‘-1’ is transmitted to signify a NACK. When acknowledging a multi-user packet, a ‘1’ is transmitted to signify an ACK and a ‘0’ is transmitted to signify a NACK.

  7. Data Channel

    The Data Channel is the channel on which data is transmitted. Table 5-42 shows the types of modulation used to transmit data. Subtypes 0 and 1 use only B4 modulation. Subtype 2 may use any of the defined modulation types; the type of modulation used is dependent on the rate at which the data is transmitted.

Table 5-3 Data Channel Modulation Formats

The Reverse Traffic Channel used by subtypes 0 and 1 is the same as is used in EV-DO Revision 0. The Reverse Traffic Channel structure used with physical subtype 2 is shown in the following figure. RFmx Waveform Creator does not perform the encoding, scrambling, interleaving, and repetition contained in the gray region.

Fig. 5-18 Reverse Channel structure for the Traffic Channel

EV-DO Revision A Forward (Downlink) Channels

The forward link consists of three time-multiplexed channels – the Pilot Channel, the Traffic/Control Channel and the MAC (Medium Access Control) Channel. The following figure shows how the time multiplexing of these channels works on a slot-by-slot basis. Each slot has the same structure and there are 16 slots in one frame. If no data is transmitted, the slot is inactive and only the Pilot and MAC Channels are transmitted. The slot structure in the following figure is used in all of the three physical subtypes.

Fig. 5-19 EV-DO Revision A Forward Link Slot structure

The channel structure used in physical subtype 0 and 1 is shown in the following figure.

Fig. 5-20 Subtype 0 and 1 Forward Link Channel structure

The channel structure used in physical subtype 2 is shown in the following figure. RFmx Waveform Creator does not implement the encoding functions contained within gray areas. The Traffic/Control and Pilot Channels operate in the same way in subtype 2 as they do in subtypes 0 and 1. The MAC channel used in subtype 2 is considerably different to the MAC channel used in subtypes 0 and 1.

Fig. 5-21 Forward link channel structure

Forward Pilot Channel

The Forward Pilot Channel is transmitted in the Pilot Burst of each half slot and is used by the access terminal for initial acquisition, phase recovery and timing recovery.

Forward Traffic/Control Channel

The Traffic/Control Channel is transmitted in the two Data Bursts of each half slot. It is a packet-based channel with a variable data rate. The following table details the data rates and modulation parameters used in physical subtypes 0 and 1.

Each physical layer packet can be preceded by a preamble sequence whose length is dependent upon the data rate. The preamble sequence is determined by a MAC Index value. In subtypes 0 and 1 the Mac index is in the range 0 to 63, whereas in subtype 2 the MAC index is in the range 0 to 127. The preamble is a repeated bi-orthogonal sequence that uniquely identifies the destination access terminal. Physical subtypes 0 and 1 use a 32-chip bi-orthogonal sequence to encode the 64 possible MAC indexes. Physical subtype 2 uses a 64-chip bi-orthogonal sequence to encode the 128 possible MAC indexes.

Table 5-4 Subtype 0 and 1 Forward Traffic/Control Channel

Modulation Parameters

The following table details the data rates and modulation parameters used in physical subtype 2.

Table 5-5 Subtype 2 Forward Traffic/Control Channel Modulation

Parameters

When a packet is transmitted in more than one slot, a three-slot spacing is used between each slot. Physical layer packets for other access terminals (users) can be transmitted in these inactive slots. When multiple packets are transmitted to the same access terminal (user), a three-slot spacing is used between the last slot of a packet and the first slot of the next packet. This gives the access terminal (user) time to acknowledge whether the packet was successfully transmitted or not before the next packet is transmitted.

Forward Medium Access Control Channel

The Forward MAC Channel is transmitted in the two MAC Bursts of each half slot. In physical subtypes 0 and 1, the MAC channel consists of three sub-channels — the RA (Reverse Activity)Channel, the RPC (Reverse Power Control) Channel and the DRCLock (Data Rate Control Lock)Channel. The MAC channel used in Physical subtype 2 consists of the three sub channels used in physical subtypes 0 and 1, and an additional sub channel, the ARQ (Automatic repeat request) channel.

The MAC channels’ symbols are spread by an orthogonal Walsh code and transmitted on either I or Q. In physical subtypes 0 and 1, 64-chip Walsh codes are used, whereas physical subtype 2 uses 128-chip Walsh codes. Each Walsh code corresponds to a specific MAC index. The following figure shows how MAC indexes are mapped to Walsh codes in physical subtypes 0 and 1.

Fig 5-22 Subtype 0 and 1 Walsh code to MAC index mapping

The following figure shows how MAC indexes are mapped onto Walsh codes in physical subtype 2.

Fig 5-23 Subtype2 Walsh code to MAC index mapping

The RA channel is transmitted on a fixed Walsh code corresponding to a MAC index of 4. The RPC, DRCLock, and ARQ channels use the MAC index to uniquely identify the destination access terminal (user).

The bits produced by the RA, RPC, and DRCLock sub-channels are BPSK modulated before being transmitted on either I or Q. The ARQ channel consists of three parts:

The L-ARQ (Last ARQ)

The L-ARQ is sent after the final sub-packet in a packet is received. An ACK is sent if the packet can be decoded, or a NACK is sent if the packet needs to be retransmitted. The L-ARQ is sent using NOOK (NACK-Oriented On-off Keying), where an ACK = 0 and a NACK = -1.

The H-ARQ (Hybrid ARQ)

The H-ARQ is transmitted after a sub-packet that is not the final sub-packet of a packet is received. The H-ARQ sends an ACK if the packet can be decoded, or a NACK if more sub-packets are required. The H-ARQ can be sent using either BPSK (Bipolar shift keying) where an ACK = 1 and a NACK = -1, or AOOK (ACK-Oriented On-off Keying), where an ACK = 1 and a NACK = 0

The P-ARQ (Packet ARQ)

The P-ARQ is used to acknowledge that a packet is successfully received. The P-ARQ is sent using NOOK.